Why the **** do you loose LP in ranked when you have TWO D/C players for more than half of the game?

Why the f*** do you loose LP in ranked when you have TWO D/C players for more than half of the game? This. I just lost 17 ******* LP because of two morons that just left game, one after dying twice mid, other because he was "lagging" and feeding mid as well. So both premade? In any case, we somehow managed to hold out 3 vs 5 until they eventually won ofc. So I was like, "Ok thats fine I'm sure riot has SOME KIND OF SYSTEM to combat this sort of cancer". TURNS OUT I JUST WASTED A WHOLE PREVIOUS ******* HOUR GAME AND LOSE ALL LP IN THIS ****.

Why haven't they thought of something already when you have so many D/C in ranked to not make you loose LP OR AS MUCH????????????