Punishing people in ranked for afks on their team.

I've never been one for ranked until recently, and I've been playing since season 3. In the past week, in so many of my games, I've had people afk or otherwise disconnect mid-game, giving my team little to no chance to win. My issue is that these people that are playing great and trying their best and being good team mates are being punished for someone leaving their match. Why has this issue gone on for so long without Riot doing anything for the players whose ranks suffer because someone else decided to be a jerk and leave a ranked match? Just a few days ago, I went from 0 LP to promos in one day, then lost 3 matches later that day just because people decided they wanted to leave, so I'm the one that ends up losing promos and LP, even though we could've won, had someone not left the match. People leaving matches and nothing being done for the people actually still trying in the match makes me not want to play league, let alone ranked, very much at all. Knowing that one person leaving could ruin my ranking without me even having a chance to win the match is just a really all around crappy feeling.