For me, it was the sense that you couldn't spend your gold pieces on: merchant ships, retainers, fancy clothes, castles, bribing people, hiring people, armies, boozin' & wimminizin', etc. etc. etc. unless everyone else bought into that idea (including the DM and the CR system) because then you were mechanically behind anyone else who toed the party line of gold=resource gained from defeating enemies, used to improve your characters stats and abilities. We already have a resource like that, it's called xp (used to come along with the gold at a near 1:1 ratio. If gold becomes that, then you can't unabashedly use it for, y'know, gold things.