Personal anecdote: when I was single in a big city, I stayed at home playing games on Saturday because I had no social group with single people in it and no place to hang out other than a bar.
Bar culture always sucked (and still sucks) and I wasn't pretty enough for Tinder. The music scene I was involved with was fading out and I wasn't part of the core clique anyway.
Would I have liked to go out and meet people to have casual sex with? You bet I would have. But it was such a chore to even put myself in a position where such a thing was even a possibility (make new friends who hosted parties and invited single friends? go out and take nicer photos for a dating site?), that it seemed like it wasn't worth the effort.
The flipside is that, while I was at a 4-year university with a nice campus, the setup for making connections for casual sex was a lot better. But I also was a lot more willing to put myself in weird grimy situations, so I don't know if it's a fair comparison.
Moral: beware the direction of causality. Some people aren't having casual sex because they are gaming. Other people are gaming because they aren't having casual sex, whether it's by choice or for lack of opportunity.