Pluggability is very hard. Different version control systems have entirely different concepts of revisions. It's very obvious, and much worse, when an IDE has

Pluggability is very hard. Different version control systems have entirely different concepts of revisions. It's very obvious, and much worse, when an IDE has plugins for VCS, as often the VC concepts aren't mapped well. When original git integration came out it was often terrible, because it forced git to behave like SVN. I'm not saying we should tie ourselves into a single VCS, but tight integration has lots of benefits, and pluggabilty while maintaining those benefits is harsh bordering on impossible.