Because they left the game, in general, although "quitters" might be a more appropriate description.
Also maybe someone fix the wining / losing streaks shown in records?
http://dotabuff.com/players/92837832/matches?page=29
How do I have losing streak of 10?
კომენტარის დასაწერად გაიარეთ ავტორიზაცია.
How about, fixing it?
By that I mean, not counting any game that has more than a leaver.
I don't want to check someone's records to find out he has a GPM record of 1000, where he had 2 or even more leavers.
I am sure the amazing developers can implement this easily :D