Why is verbal abuse even reportable when there is a mute button?

Yes, I've gotten heated, I've had a couple of 10-game restrictions. I'm not in one now, so this post isn't spawned from an active or recent punishment.

But I honestly don't understand why verbal abuse is punished with the severity that it is. I've had games where my constructive comments were reported and used as justification for my 1-0-game restriction. I'll never forget one game, the worst thing I said was "please hug the tower, you're dying too much, we can win later on just forgo the CS." Boom, someone's feelings got hurt.

But you can mute and make it all go away. On the other hand, I can't press a button and reclaim the ELO that a leaver triggers onto me, I can't press a button and make a teammate who abandons his lane in order to grief - and who declares as much in chat - go away or restart the match. And yet these offenses which impact actual ELO and not just someone's feelings are among the LEAST punished by Riot, because the AI can't detect it unless it's the most egregious of offenses.