Why doesn't Riot introduce a good loss forgiveness program?

Seen a bunch of threads about this and how people would abuse it, like if they started to have a bad game that they would just go afk. In my personal opinion a REAL simple solution to that would be to just ban people who afk and forgive the rest of the people who get a loss from a 4v5 the entire game. Not saying that it should be a one time thing but say someone goes afk 5 times a month they get banned or something like that. Or do like 3 times a week = 1 day, repeat = 1 month. Personally I would much rather get a loss than get banned and yet every few games you get someone going afk because absolutely nothing gets done about it...