There are several reasons why this trend exists:
- A villain, in order to be threatening, must want something, and have some chance of getting it.
- Most heroes are protectors of some kind (cops, doctors [in medical dramas], or the parents of children who are being threatened by some [possibly supernatural] evil) and the villain's plans are a threat to the hero's Protectorate, thus making it impossible for them to be unusually proactive before the story starts.
- If the villain doesn't do anything, the audience is entirely within its rights to think that this is a case of Orcus on His Throne, which is frequently felt to be a bad thing.
- It's easier to write another story (and given that much fiction nowadays is in some form serialized) if the hero is not the one responsible for everything happening. Less important in one offs.
- The Heavy is in full play here, as well; and one of the few ways to make a smart villain appear effective is to have him be a successful schemer.
- If the hero is proactive about his situation, then the Status Quo will, in most situations, eventually change, which is frequently banned under Status Quo Is God.
- If the hero actively opposes the villain before the latter has done anything evil, all the audience sees is a Designated Hero harassing a Designated Villain for no reason. Less of a problem for running series where the villain earned his reputation in previous stories, though that can be seen as a belated heroic reaction to the villain's past actions.
Aversion of this, Heroes Act, Villains Hinder, comes from stories centering on the actions or emotions of the hero:
- The Villain Protagonist, obviously because they are the ones with the Evil Plan but this can vary.
- They may be against the Hero Antagonist which is this trope from a different viewpoint.
- A Big Bad who is Eviler Than Thou may show up which means that both The Protagonist and The Antagonist can be proactive AND reactive. This can result in a Gambit Pileup towards the end of the story as both character's schemes come to a climactic, and sometimes catastrophic, resolution.
- Variations on To Be a Master which require the hero to go beat up the other masters to claim the title. A variation in that the "villains" are not necessarily evil, and may simply be fellow competitors who want the same title the hero does.
- Some forms of The Quest, like "Hey, I found a treasure map!"
- Slice of Life
- Rags to Riches
- Great Escape (though it can also be considered a reaction to being imprisoned)
- Perpetual Poverty
- Any story set in a Villain World where The Bad Guy Wins and the hero must reverse this outcome.
This trope is much too broad for examples. Try the subtropes instead.