Why no Champion Mastery for 3v3 and ARAM, Riot?
You're giving Champion Mastery points for playing a champion in temporary funmodes, but not in 2 out of 3 permanent gamemodes.
Is there a good reason behind this other than laziness? The only one I can think of is that you want to prevent people from spamming these gamemodes to get mastery points. However, you could simply reward them with a reduced amount of points if that's the issue.
Do you not want to promote these gamemodes? I enjoy both of them, but I currently avoid playing them because I want to get champion mastery points.