You're just hurting yourself in the long run though if you don't upgrade your helmet. Also in regards to trading, I think not implementing it was another way of Bungie trying to artificially extend the life of the game. It makes players play longer to hopefully get that gun or armor piece they really want. I could have full CE raid armor on my characters by now just by trading my unwanted exotics I have sitting in my vault, thus making me want to run the raid and play the game less until the next expansion.