Why does riot rematch people that youve muted and reported in the previous game?

like, this happens so often and i have no idea why you would allow that in matchmaking. Previous game the adc was a total asshat, flaming and blaming everyone in the team, spam pinging, emotes, the usual stuff. so muted reported in post, next game i get requeued with him, and surprise surprise, he steals my blue at level 1 and emote spams.... and goes on to give away first blood and blue to enemy adc... why would you intentionally ruin a second game where 2 people clearly hate eachother? all it does is make 2 games bad for 10 people.
Report as:
Offensive Spam Harassment Incorrect Board