A lot of these things are in the DM's purview but should be touched a lot more on by designers in supplements about warriors/weapons and DM material such as the DMG. To be honest when it comes to world building there are a lot of areas that don't get touched upon that would lead to very different games.
Its not a world building issue. You can pretend all you want that maces are better against armor, but when the rules do not support that then they are in the end not.