It is a bug. It is, believe me! The same crap also happens in cross-faction pre-made matches, where I know for certain that my team mates don't bypass Need or Greed.
Not only because I trust them but because they dont need the, almost always crap, drops.
Vornek here has the right of it (especially the bit about crap drops): it is a known bug, and Brandon, as the community rep, has assured us that the devs know about this bug and that fixing it is a high priority.