I’d argue many super-heros actually embody a social force for good, which is depicted through the actions of a single person for practical writing reasons. When Captain America finds himself out of the Avengers and fighting against the government, it’s not vigilantism but thinly-veiled political commentary.

Of course what you describe also happens, and lots of the times it ain’t that deep. But I wouldn’t say it’s “all super-heroes”, and Batman stands out a lot for me with his ultra-individualistic values (at least among the mainstream superheroes).