Some people might have some GitHub repos with games and game engines written in Nim.
Some people might have even shipped some second tier game written in Nim.
Then again, hobbyists will use anything.
But virtually nobody had used or uses Nim to create any kind of game or game engine that is behind any successful game in the real world.
I need to remind people that Minecraft, a hugely popular game in the "real world", was originally written in Java. Not the kind of language you'd expect a game from. (I will agree that Java is probably not the right tool for the job though ^^').
This is the kind of thing where nobody will use it, until someone does. And proves the viability of the language. Nim has the potential to be a good gamedev language, but lacks the maturity.
Wishful thinking doesn't have a place in discussions on the technical merits of a technology.
It's like everyone is stating that the bugati veyron is the best car ever made and your only cobtribution to the discussion is making claims on how your flying car is way better.
Besides, flying cars are way better. We need to keep looking into the future, otherwise we'll be stuck with what shitty technology we currently have.
The GC is optional. It's also configurable and there is a realtime garbage collector, too.
Finally there's also region based memory management.
https://nim-lang.org/docs/gc.html
https://forum.nim-lang.org/t/2489