Why does steam need to run as system? I'm wondering what privileges steam needs on Linux

Ever since I gotten myself a Steam Controller I’ve noticed my distro has restrictions on USB IO preventing the controller from being updated through the Steam client without root/sudoers access. The Steam client itself has never prompted for root access but the script used to update the controller certainly requires it, at least on Debian based distros, can’t say it’s like this for Arch based as that’s what SteamOS uses.