The existence of a GC, even when it can be turned off, does preclude a great many other possibilities, in practice. One issue which is nearly universe, and extra bad in Go, is the extra cost of FFI with C libs, which is necessary in games to talk to opengl, or sdl2, or similar.

If you aren't going to use the GC, then you open up a lot of other performance opportunities by just using a language that didn't have one in the first place.