While i don't personally play TT that often myself, i know that there is still a portion of the community who do. While this isn't necessarily me asking for a change, i would at the least like some justification or reasoning from a rioter, or a link to where they did say why. That is all. EDIT: 1st comment answered me lol. nvm
ARAM player here. Feelings a little hurt, considering the ridiculous amount of money I spend on this game. Hopefully we won't be left out forever.
I guess on the plus side, by the time we get champion mastery, it might actually do something. Like chroma unlocks or icon rewards or whatever.
Disappointing that it's not on TT or Aram. Be nice to know WHY it's not enabled for that. Sigh.
They said that during the start it would only be enabled for Summoners Rift matches and they'd enable it for other modes in the future. They did this to make sure it was stable and all.
That's a bullshit reason and they know it. Theyre waiting to see how many people they can pull over to 5s before they activate it in other playlists if they even do. Its known that riot hates 3s and wont do anything with aram.
5 Months and still no progress for at least Ranked TT? I have a friend with 3 mastery points and 3 SR games played, even though we have a gold 3's team... 
Personally, the whole champion mastery implementation is a way to display and show your experience and skill level with that champion. If I had to guess, and this is just my opinion after all, it's implemented onto SR with certain algorithms in mind based on in game stats. Whatever it's graded on is currently limited to SR. Whereas, with other game modes it wouldn't match up equally. Like, if it's based on KDA to some extent it's known that SR matches are typically more strategic whereas the TT meta is more skirmish based. Which means, more roaming and less farming. If it's based on Barons/Dragons, etc. well, that would change a lot of grading in other game modes as well. What about standard match times? Different for each game mode. Arams everyone is bound to die at least once. There goes your perfect S score. You get the point.
Hopefully it's going to be contributed to other game modes, seeing as I play rank 3v3s commonly and is the only time I find myself playing mages. Aram would also be a nice touch, just because it still provides experience on a champion, but to a different extent. Obviously, the weight of points should be lowered, not too dramatically, but a tad. But should still be given some at the least just for gaining experience on a champion.
Sometimes, Aram would even be the only way I level up a specific champion at all. So to have a number value input into the mastery system for that champion showing that I've actually touched them at least once, would be a nice addition. Especially since it's entirely random after all.
Is Mastery something 3v3 players would even want? Considering how badly they messed up the Dominion score system, I wouldn't trust them with finding relevant data for 3v3. Mastery sounds like a bad idea to me, and it's likely they'll mess up the scoring system in some ways, so 3v3, ARAM, and Dominion might be better off without it.
