Regardless of whether or not you win, JiP doesn't not work with a skill based matchmaking system, period...
Sure, not EVERY person that quits does so because they were losing, but anyone who's been with Halo knows that it's a very common, if not THE MOST common reason for quitting. Regardless of the reason, it gives the joining person a less than ideal experience...
And the TitanFall comparisons just don't work... It doesn't have skill based matchmaking... The player that joins could be the best player in the world, or a noob... In halo, it supposed to be a guy at your level, so the chances that he'll be able to dig you out of a hole are slim...