Why can't Champion masteries be private or set to private

It is no discussion that the community and the people who play this game are generally negative and find any reason to blame bad games on everyone but themselves, usually their team. I speak for myself but the champion mastery thing seems to add fuel the finger pointing.

Mind you all this is the opinions of someone who goes into NORMAL DRAFT without friends or a group to filter out the randoms.

So, I enjoy playing specific champions because they are fun. I might not be good at them, but they are fun to play and how does anyone get good with a champion without playing them a ton(?). So an example of the mastery thing being a problem, for me at least, is if you are not doing well or just dying a lot, one or two people will use your champion mastery as a scapegoat for the game. "omg lvl5 Ahri so bad" or "you are lvl 4 braum but it's like your first time or something" blahblahblah. I'm aware that mute exists but when you have to mute almost every game you do bad in or every time something like that crops up, it gets a little taxing on the psych to the point that I'm afraid of playing some champions because I just don't want to deal with my team's crap if I end up doing poorly.

THE POINT BEING if the goal is to have fun, champion mastery being made public feels like it does the opposite effect. It is a whole different story with 'ctrl 6' in game. But if the banner and stuff can be private and for your own personal enjoyment, rather than in everyone's face in the loading screen where assumptions are immediately made, that would be nice.

Them elo standards are starting to tire me out so here's mah rant on why rito is "such bad company" or something like that.