As I understand it, this behaviour is because of the co-op nature of the game. There are other things that don't work unless they are on the speaking character, like gold at vendors. Additionally, when you Sneak, only that character Sneaks, rather than the entire party.
It annoys me as well - moving gold from character to character so they can buy or repair or identify items is tedious.
It would be great if the game treated linked characters as one unit for these things.