i just think they are afraid that they will realise the game has never been perfect and other people would enjoy some changes, that people always wanted but never had the chance to get.
afraid that if we got to chose shared or personal loot before creating a game wery few would join their shared loot games.
just theorys 
many people have a harder time making and keeping friendly contacts with other people, thats maybe why they play video games? who knows, everyone is not good at making friends or socialy awkward. its harsh to always play with new random people who maybe dont have any urge for helping and only have them or a friend in their mind.