Authors can use this trope to comment on the use of Planet of Hats, and how the "hat" defines the job(s) that will be excluded. While Planet of Hats enables authors to pick out a particular aspect of human society and human psyche, this trope enables a focus on what that particular aspect doesn't value or even actively hates.
Normally with the Planet of Hats, the hat fitting to the local standards also defines the measure of respect and vice versa: they all wear the hat because it's what gives some prestige. Conversely, anyone not wearing the hat or a hat that conforms to their idea of what gives prestiege are by default dishonorable and worthy of contempt.
For example: if the greatest honor is besting someone in sword-to-sword combat, knights get the most respect, pikers and lancers get a modicum of respect (bladed weapon, albeit not close range) and squires are looked at with something between neglect and appreciation. The smith who made the sword is at too many removes to even be considered part of the prestiege earning activity (never mind the iron miners and farmers). And since they aren't on the battlefield at all they're considered with contempt for being "cowardly" or "talentless".
If this trope were applied without a Planet of Hats, then it would become Acceptable Targets: careers. The reason being that a prejudice applied against a profession by a society that has no rigid value structure for professions isn't putting people down because their profession isn't perceived to contribute, but rather because their profession itself is found generally distasteful.