A way that people are using to get around bans

So I just finished a game of Team builder with some friends (we lost sadly), and I was stuck bot lane with a caitlyn that had an interesting way to get around a potential ban threat. She started off the game by shouting that she was going to mute everyone, then apparently proceeded to do so. She then mentioned that she would be using pings to communicate (not too much of a problem, that's why they're there). Then the kicker came that she essentially refused to communicate with the team and proceeded to solely farm and get dragons/die to baron for the rest of the game, occasionally using her ulti to snipe kills. So because she was doing this tactic, she ended the game with the most farm out of anyone, a 2:1 kda ratio, and seemingly having done nothing wrong. But the problem lies that this person is aware of this fact, and even mentioned that there should be nothing wrong with simply using a button built into the game (could be either the ping tool or the mute button, wasn't able to wring that information out of them), and that there's no reason they should be banned. Now me and my friends all reported her, but obviously she is not new to this behavior, so this begs the question, why is this sort of behavior allowed when it is far more toxic than simply running headfirst into enemies?