So this is really a meta meta question, but here it goes...
I've noticed that Meta StackOverflow has for a while now been used as the meta site not only for StackOverflow but also for Area 51 and more generally Stack Exchange? Back in the days when the trilogy were the only SE sites, this was just about fine. However, I can't help but feeling it's slightly inappropiate to be be posting questions about Area 51 related topics (or even more general) on this meta site, which should really cater only for StackOverflow judging by its name.
I notice there exists a meta.stackexchange.com site, though this doesn't seem to be used nearly as much. It also seems to be running a slightly older version of the SE platform. So the question is, why don't we have a meta.area51.stackexchange.com site? Similarly, why don't we use meta.stackexchange.com for questions relating to the platform/all SE sites instead of this one?