There isn't enough variety of gear in destiny to justify trading. Trading would kill the game so much faster than any other changes. Even those who want it would, once they had traded and acquired every item in the game, then played for a month just for the fun of it, then lose interest. This game is fun in and of itself, but it's chasing loot that keeps you coming back to the same content literally hundreds of times and still getting excited when you get a good drop.