Because the other team has earned the right to stomp that team out of existence. Just because a few bums leave early, or get disconnected, doesn't mean you get to start with something that can shift the outcome in your favor even though you've come in late against your own choice. Take your ass pounding, grab the rewards you still get regardless of the outcome, and hope you get a fresh match in a few minutes. If winning mattered, maybe there could be a different discussion. What I think is a bigger travesty is Bungie errors removing you from an activity when you had full special/heavy and then when you renitence you're back to zero. That is truly -blam!-.