Storm Troopers always get grief about their armour not protecting them but I've never felt that it was the main reason they wore it. Taking away a troopers individuality is why I think the armour was worn....it was the Empires way of saying hey your not a person you're just a piece of equipment that can easily be replaced. In battle orders would be followed without question by the Clones because there was no personal attachment between the men....when one faceless trooper fell there was always another one to take his place. As for the other sets of armour in the galaxy that was worn more as a statement by the person inside it and not for any protection it gave....would Boba Fett have become as popular as he has if he was wearing Landos outfit from Cloud City?! I can't recall anytime in the Saga where any armour really did anything besides looking cool?