Well, it usually installs from source, but that's not really the point. It's a package manager, it is trivial to give it it's own home, (and thankfully they made that an easy thing to do), but to throw it in that /usr/local bucket by default? It seems like a decision that requires real justification and the reasons I have seen seem pretty weak.

I mean, in the end it seems like almost nobody cares, but it's always been a pet peeve of mine.