If you join a regular high level dungeon for example the item level range starts at 50 but has no limit. A 110 item level character over powers the item level 50 so much the balance of the party system is changed, like DD taking all hate from tank. People have posted they don't like carrying players lower level then this would solve that and make party fighting setup normal. Brackets of level keeps you synced in a manner of not totally over powering the other party members.