The back paddles aren’t mapped to anything by default and there’s nothing Steam can do to help there. There are also some vibration levels you can’t set elsewhere and having a hardware switch for different profiles is nice.
The back paddles also can only be mapped to other buttons that are on the controller so I need different profiles for different games. I usually map them to l3 and r3 but sometimes its nice to have them as b and y instead without having to mess with steam input.