Players disconnecting after the match starts, and we cant remake?

Had 2 games where that sort of thing happend (Last one: https://matchhistory.eune.leagueoflegends.com/en/#match-details/EUN1/2283431011/225934213?tab=overview)

Why is this allowed? This kills all my joy of playing this game, i was in promo for Gold 2 (first season) and i lost it cause of disconected player. He will get a ban for a week or 2 and thats a maybe, and i now have to play at least 5 more games where i will get trolls and afks in my games.

GG