Why don't I get chat bans but just a 2 week then a perma ban

You were found to be exceedingly toxic by a riot staff member. If you jumped from no chat restrictions straight to a 14 day ban that means a riot employee was manually reviewing your reports and decided you went above just a simple chat restriction.

after the 14 day ban, you are on a higher priority watch list. one word out of line and bye bye.