Pop Culture Question

History is interesting because it sometimes develops in unexpected ways. I've always wondered for example why in US comics, superheroes became the dominant genre (DC used to stand for Detective Comics after all). And when it comes to RPGs, why the stereotypical genre is usually fantasy or science-fiction (as opposed to something like romance or the Indy RPG scene where it can be set in contemporary times). I mean I know the history of both comics and RPGs. It just boggles the mind why it turned that way(or why that genre was chosen) instead of the other alternate courses it could have taken. Are there any interests of yours which is occupied by a niche-genre?