Why does it take dozens of games to finally ban people who run down lane and AFK at tower?

The system clearly does not work if a player can;

A) Not play in the lane they were assigned. B) Intentionally AFK in front of the enemy tower after each spawn.

Only to see they've done this over multiple games with 0 penalties so far.

There are 4 other team mates that all have to suffer (While losing LP) from someone intentionally trying to make you loose for laughs. I've seen multiple posts now of players getting away with this for ages.

Everywhere I look Leagues just a meme on gaming websites for salt and "cancer". That's normally a sign there's a problem especially when you're famous for how toxic your community is. I've been playing since 2011 and it's actually getting worse somehow...