Yeah, they're crazy popular. Old genre too, goes back to at least the '90s (though mostly in Japan), and probably older. The reason you're not aware of them is

Yeah, they're crazy popular. Old genre too, goes back to at least the '90s (though mostly in Japan), and probably older. The reason you're not aware of them is probably—assuming you're a guy—because they're mostly played by women (especially the ones that aren't outright porn—though, those too). They're particularly popular on mobile. If you've ever seen the stats about how there's a huge number of "women gamers" and been like "wait, if there are so many, where the fuck are they?" it's because a large proportion of them mostly play dating sims and visual novels (often those two have more than a little overlap) and other game genres that you don't, like casual browser games or puzzlers. It's similar to why the average woman can name more romance novel authors than the average guy can.