Gentoo is now #22 on the distrowatch list ;-) When I first started using Linux, it was 7.
But the thing about Linux is that it is easy to install dependencies. Torcs isn't installed by default either.
I know there is fear (and ignorance) about Mono, and many other things, and we will not fix these problems today.
It is defenitely not installed by default in Gentoo (I know that because I use
that). Most distributions give the possibility to install it. I know from
Debian that packages are removed from main Gnome applications because it
required Mono (and not everyone wants Mono).