Why should they? Tor is managed by the Tor Project. It is bundled & shipped as TBB already, using Firefox. You already can use it if you want to, so why would t

Why should they? Tor is managed by the Tor Project. It is bundled & shipped as TBB already, using Firefox. You already can use it if you want to, so why would they bother with implementing Tor in the mainstream version of Firefox? They could only offer it as option (because not everyone wants to use Tor all the time) and this option is already satisfied.