Why is it that people who troll games are so difficult to punish?
Actual trolling it a lot harder to detect then reading through a chat log. Unless you are including timestamp and description in your report then the entire game has to be reviewed... Then they have to take into account the possibility that the person is just bad/having a bad game or playing off meta neither of which is punishable.
While intentionally feeding seems like it would be easy to detect it really isn't...... unless the person is literally running under tower to feed and even then sometimes it is just a bad turret dive..... so once again the entire match has to be reviewed..... Where as with verbal/chat toxic behavior that can be read in a matter of minutes by a person.....(even faster when a lot can be automated for chat restrictions)
On top of this, why are they punished less often (from my experience, could be wrong) than flamers?
Having a bad game or choosing off meta is not trolling. A huge % of the time people complaining about a troll is because someone had a bad game/chose off meta.