AFK PLAYERS

I lost my promos because one guy left the game in min 1 and never came back,now i got demoted because my adc left in 30 min,we lasted for 15 more min but their split push was enough to end us. In 10 games i would say i lose 6 because someone leaves the game,i dont know if they have net issues or whatever, but why does that have to be my problem? why do i lose my time,lp,promos etc. because someone else have pc problems? Why dont we get loss prevented when this happens? Its just unfair to play like that because its not my fault i cant control it...