Well it could potentially open up the floodgates for potential complaints leading to people wanting ''requirements'' before being allowed to join matchmaking. Witch could lead Bungie's development being split even more and less would be done on the game. That's at least 1 argument I could see.

And a giant meteor could fall from the sky or we could get hot by a bus every time we go outside, so the same line of thought would suggest everyone be forced to stay inside to protect them.