why do people always never try to end the game?

I hate league because if I do good and I am fed, my teammates start loafing around. Instead of grouping to win the game, there's always someone trolling not wanting to win. Like my last game where I played quinn. Literally the jax purposely never grouped and everytime we told him to group he would say no i want to 1v5 and win. Fuck you, you are a piece of shit. You cost us the game because you want to mess around instead of group and win. Meanwhile the enemy team they got shit on my be all game so they started grouping and since they are grouped, it only takes one person to stun me and im dead while jax is afk farming the jungle. I reported but i know he wont get in trouble too which is stupid. Post game, he says i was toxic even though he purposely threw by never grouping while the enemy was grouped and killing our team.