Why am I forced to play a game where my teammate loads in then DC's

I'm dumbfounded that our team is forced into playing a 4v5 when one of my members loads in, buys his items, then DC's for the entire game. My midlaner at the end of the game literally had 0 cs and was level 1 for the entire game because of DC, however we weren't allowed to remake. At the end of the match I still lost my LP even though it was a 4v5. This is dumb and drives me away from playing this game.