Look at all the pro gamers; they aren't bringing their mouse every where they go, they just save their settings rock in another mouse and are ready for gaming.
You would bring your own mouse, however when you sit down at a tournament machine you will need to install specific mouse drivers and get it configured. Being able to sit down at any machine and just plugin your mouse/kb and have a familiar setup seems like a great idea to me.
Correct, pro-gamers (and amateur competitors too) will take their mouse to any tournament, and if they forget it they will try to find the same model to use.
Pro gamers are the only people that would do this. No one else, using gaming mice like these, move around enough to locations guaranteed to have their mouse on the premise to justify this sort of behaviour.
It depends where you are in the world. I believe they're exceptionally popular in some parts of Asia like China and Korea. In places where everyone has a personal computer powerful enough for everything they do with it, and with a tablet/laptop just about every cafe is an internet cafe.
Even still, there are niches to fill in such places. Relatively recently (last year I think) a place here opened with exceptionally high performance PCs/net connection, comfortable chairs, etc, which focuses on gaming. Every time I walk past it's packed, so they're doing something right.
