Trading would ruin the game. Because really the only reason a lot of us play still is because we want to get the loot, and if someone could just give it to you then there would be no reason to play
Then think around it... not hard to do that. My solution to add it instead of keeping social interaction limited: limited trading. Trading gear only of equal value and obtainability. Raid weapons only for raid weapons, exotics from drops or Xur only for exotics from drops or Xur, exotics from the raid only for exotics from the raid. I always need trading. Relying on RNG isn't really fair either, since it's random and not entirely effort.