How are so many people who don't care about winning allowed to play ranked?

Literally almost every single game, there is at least one person in the game (whether on my team or not) that just thinks the game is over and just gives up/throws it purposely. It's beyond obvious that they don't give a damn about winning, whether it be through their "gg ff15 im afk in all lane gl", or their obvious trolling, to the straight running it down. There are SO MANY players that make it so obvious, yet they are still in almost every game I play?

It feels so meaningless to win games against trolls, and its just infuriating to lose games due to trolls. Especially when your team is like 32 kills to 10 but the one person that didn't have "their" way is just like.. nah time to force a loss.

These people are just blatantly ruining the game for everyone else with no respect for anyone but themselves and it sucks. LP feels almost meaningless when you lose/gain so much because of these types of people running rampant knowing that there is no punishment coming to them that is severe enough to actually fear. It's ridiculous. And it happens way too often.

It ruins the game for so many people that want to try so hard to enjoy it.