It’s not boot time, but context switching (close apps and whatnot). I suppose I could hibernate, but I still lose access to my network services, like my kids’ Minecraft server and network shares. And then Windows usually has massive updates because I launch it so rarely.
If I play on Linux, I just launch the game, and that’s it.
Before Steam came to Linux, I just didn’t play games very often. Now that most games work, I can just push play and I’m in a game, so I play a lot more games.