2v2 Team mmr's not equal

2v2 Bnet match making algorith. In 2v2 it seems to pair (based on MMR) two high ranking partners together and then the two lowest ranking players together. What I would expect to happen is one lower ranked player would be paird with a higher ranked player. So both teams would have a combined mmr score that equals each other. Am i missing something? Is there a reason why they pair the two higher ranks together and the two lower ranking players? What seems to happen is as soon as people see the mmr of the two teams the lower ranked team just leaves the game as soon as it starts. And I cant blame them. I would expect the match making system to try and make the teams fair. Am i missing some unseen stats being used in the algorithm that would suggest the way it is is the intended result Blizzard had hoped for?