People just like to dunk on things to make themselves feel better. And this can be especially a thing in gaming because lots of gamers are badly-adjusted and desperately need to feel better. It’s nothing really to do with mobile games specifically at all, you see the same thing with anything outside of the very narrow window of “real” games ie the games these people happen to be into.
It’s one thing to have a preference, it’s quite another to look down on other people for having a different one. We’re all just choosing to spend our time staring at pixels on a screen.