Why is LP based off of Win/Loss?

Basing LP gain off of Win/Loss doesn't seem right for placing someone in their ELO. If a player is feeding or trolling and it causes us to lose the game why should we lose LP for something they did? It should be mostly based off of personally performance with win/loss making a very small effect in the gain or loss of LP. It should mostly be based off of CS, KDA, Wards, Damage Dealt, etc in my opinion. Just my thought and I think this would help with people getting in their ELO and not losing LP for someone else feeding.