So is D&D Skyrim etc. Just because a game is a RP game doesn't mean everything is left to the player. Part of the reason to implement this would be for atmosphere. When people do RP their armour, in my experience 80% of them RP having some ornate full plate, even when they are a dirt poor knight of a few weeks in game.
Because their parents are important people, and probably made sure to scrounge up enough gold to properly equip their children before sending them out.
I personally never roleplayed as wearing full armor, nor have I seen many people roleplay such things either.
