No Game Review for Perma Bans?

I understand I can't bring my account back or anything like that, but I had my account perma banned today. I don't think it was perma ban worthy, maybe a chat restriction at most. But what confused me is as soon as I got out of the game I got perma banned. I think the bot picked up on what I said to a Nasus which was "You just called me a drunk retard" I also said "Shut up please Kayle and play" and if that is worth a perma ban then why isn't half the player base banned? I haven't had any bans, warnings or anything for this account and what I said which the bot picked up was me quoting what a Nasus said about me and my bot premade. Why isn't he banned? Why isn't the Kayle banned for called me the N word? Why isn't the enemy Rumble banned for calling everyone on my team useless b*******?

I just want to know how your system works and why you don't personally review perma ban games...