thats not the point, you've farmed lala 20 minutes ingame, some1 drops others concede game is over.
Well that certainly sucked, i just bought my ashkandor! might aswell let me finish the game 
-> concede = game ranked but will be played on, and its allowed to leave.
-> leave game = penalty + concede
->finish game after concede = a weird feeling of satishfaction due to being able to FINISH your game instead of having it cut off when the oponents decide to concede
theres a simmilair problem with FF-ing in DOTA, you've finally gotten strong, won a teamfight BANG 5X FF in your face, every1 leaves and you can't even play that fun part of the game.