There are numerous subtleties to this trope depending on the degree that you're attempting to ridicule; English, Theology, Philosophy, History, purely abstract Mathematics and other Classical intellectual subjects tend to be academically respected and prestigious but financially weak, unless when these courses are used as a preparation course for a vocational degree (e.g. Philosophy as pre-Law course). Less traditional degrees such as Media Studies are ridiculed for both their uselessness in employability and their perceived lack of intellectual importance. Vocational degrees tend to be the subject of ridicule mostly based on how respected and "realistic/concrete" the profession is; Natural Sciences, Engineering, and Architecture graduates are generally off limits, but Journalism, Political Science, and Law are fair game.
This stereotype is reinforced by the expensive value of education today. There is an epidemic of victims of student loans that could not be repaid, deterring people from borrowing cash only to spend it for useless degrees. The more the tuition fee hike goes up, the more there is a large drop in the percentage of students going for degrees in the humanities. Statistically speaking, these degrees are a lot less likely to get you a job (especially a good one) than most other ones, but is still is possible. People nowadays view education as a form of capital investment rather than an intellectual venture, hence the rise in STEM (Science, Technology, Engineering, Mathematics) Education and Business courses, which are overtaking more and more "unnecessary" subjects. In actuality, no STEM degree is really guaranteed to get a student a job (less than 2/3 of STEM graduates stay in their field), but somehow nobody mentions that: works of fiction go on pretending that students of physics, chemistry, higher mathematics, or biology can actually find work in their fields.
Another variable contributing to the fall of humanities courses is the rise of self-studying and the Internet; one can self-learn Philosophy by searching on the Internet, downloading eBooks, or living like Socrates, and one can learn English Literature in a more entertaining form through This Very Wiki. Indeed, discussing the Meaning of Life with your friends over a Sunday cup of tea or studying Hegelian Deconstruction via the media examples provided by TV Tropes may be more satisfying and cost-saving than overspending on a degree. A major in Philosophy is unnecessary to become The Philosopher; after all, Socrates and Jesus were poor and didn't need cash to spread their ideas. As a result, humanities degrees, despite being academically respected and prestigious, have acquired the same public status as Conspicuous Consumption (I have this prestigious Liberal Arts major because I'm an aristocratic emokid rich enough to afford it), and expensive colleges are reserved for more important and pragmatic courses such as Technology and Business.
It's worth emphasizing that for many, regardless of the level of personal enrichment or prestige someone may get from their degree, the typical reason a person goes to college in the first place is to get the education needed to make a decent living and avoid living paycheck to paycheck. Thanks to the previously mentioned necessity of student loans for all but the smartest or those subsidized by others, former students have a hard time avoiding substantial debt, which can make even a decent job a lot less worthwhile if it takes years or even decades to pay off loans. Of course, that's assuming that the student can find a position in the first place, in which many students don't realize just how difficult it can be to find work, assuming that just because they have a degree that employers will be all too happy to hire them, when in reality, even amongst the educated, employers often demand experience or that students start off humbly making peanuts in order to get to the positions the students assumed they would be getting. Thus, any degree that doesn't offer a high chance of a substantial financial reward to offset all this risk, i.e. the humanities, is often a huge liability and could literally ruin a person's life.
Sometimes averted in real life, at least for people who get humanities degrees from respected schools. It's not really surprising that world-changing historical figures who spread revolutionary philosophical ideas attend, well, Philosophy (of course, many of the best philosophers were double-majors and many solid contributions have been made to academic philosophy without philosophy degrees, but hey). Writers of fiction, however, tend to ignore the fact that such a thing is possible, depicting anybody who didn't choose a highly-profitable and/or Business-related major as a penniless loser, despite how many fiction writers actually had a degree in "useless". Self-Deprecation perhaps?
The increasing perception of the Liberal Arts as useless may be in part due to the flooding of the field by students who either don't know what they want to do or who simply think that the humanities are easy enough to get by (they're not), so they can enjoy the partying. This makes it especially difficult (and unfair) on humanities majors who pick the field because that is what they truly enjoy, or for educational enrichment.
Another factor is perception. As noted above, nearly half of STEM degree holders don't actually maintain lifelong careers STEM, but their average earnings are still very high. A big reason for this is because job recruiters who offer on-the-job training and thus don't really have any use for specific skills learned from colleges are still looking for the best candidates. Since STEM degrees are near-universally perceived as more difficult to get than, say, English degrees, recruiters then assume that the person who majored in Physics is either more hard-working or more intelligent (or both) than the person who majored in English, and thus would make a better employee. This is also notable for Economics majors; Economics is one of the only liberal arts majors that consistently outperforms most STEM majors (with an Economics bachelor's degree having similar median income at all levels of experience to a generic Engineering bachelor's degree), even though the vast majority of people with Economics degrees don't become economists. While the skills those majors learn are very useful for being informed, Economics doesn't teach many directly applicable job skills below the master's level; they get good jobs because banks and other companies respect their achievements and like to hire and train them.
Additionally, STEM programs are more "specific" than non-STEM degrees. A chemistry major knows as much about coding as a computer science major knows about complex chemical reactions, i.e. very little. An electrical engineer and a civil engineer can have little in common with each other, other than the word "engineer." For comparison, the liberal arts places emphasis on interdisciplinary studies. This can lead to the assumption that a liberal arts graduate is a Jack-of-All-Trades, but a Master of None. Since American universities require students to take both humanities and science classes to obtain an undergraduate degree, educated Americans have at least some exposure to both hard and soft sciences.
Liberal Arts and Humanities majors are generally disproportionally represented among student activists through much of recent history. Whether it was the Vietnam War, the Iraq War, the War on Terror, or the recent events such as those surrounding the University of Missouri, comparably few from the STEM fields were involved compared to Liberal Arts and Humanities. After all, the latter are often the best-informed about current issues and often have been presented with in-depth analysis by their professors about the whys and hows of events. From an employer's perspective, you are not only employing someone of dubious worth from the Liberal Arts, but a possible troublemaker and agitator as well. Effectively, the proposition is the possible employment of someone who not only has experience and skill at organising mass action to correct perceived injustices, but also a track record of doing so.
A few notable real-life aversions:
- Classics: C. J. Cherryh, C. S. Lewis
- History: Rick Riordan
- English: Stephen King, J. R. R. Tolkien, Toni Morrison, Beverly Cleary, Margaret Atwood, Diana Wynne Jones, Patricia A. McKillip, Robin McKinley, Douglas Adams, Amy Tan, Dave Barry, Stephenie Meyer
- Creative Writing: Colin Meloy
- Sociology: J. Michael Straczynski (double major with psychology, minors in philosophy and literature)