To preface this, I've never been banned. Never even had a chat restriction. I enjoy playing League but completely understand that I'm not that great at it, so rarely do I get the impulse to abuse someone else for playing poorly.
However, from a logic perspective, why do people get perma-banned for things they say in chat? Chat restrictions are real - why not just take away their ability to break chat rules for good instead of not letting them play at all? I personally think a ban from the game as a whole should be reserved for people losing on purpose and/or actually ruining the game experience for others.
I've played with so many toxic people who admit they're on their 2nd/3rd account due to their main being perma-banned. Most of them were toxic and awful and I hated their ability to chat with me, but had they played the game without chatting and were actually trying to win I wouldn't think anything bad about them. In fact, assuming they respond to pings and whatnot, that's kind of my ideal teammate.
Am I missing something? Do bans on toxic players really solve more problems than they cause? I'd rather play with a chat-restricted toxic guy who stays on his main account because of all the skins and rune pages and whatnot he's amassed over the years rather than play with that same guy on a new account, especially if he already has a reason (like having wasted hundreds/thousands of dollars on a banned account) to have a negative outlook on League as a whole.