Expanding the Champion Masteries System

Is there any particular reason why the masteries only apply on Summoner's Rift? I understand not having it on ARAM because the nature of the game or on Crystal Scar since games are too short and there are a lot of botters, but why isn't it on Twisted Treeline? I was discussing this with my teammates for 3v3, and they agree it should be on the 3v3 map. The same skills needed to play on Summoner's Rift carry over to Twisted Treeline and vise versa. Also, there is a ranked queue for Twisted Treeline. That means there is some skill and mastery required to play it? I think Riot should look into this as I doubt it would be a hard thing to add at this point.