The main value-prop for the steam controller was its touch pads, which allowed you to play mouse-based games from the couch (in an era when controller support for PC games was spotty). They were a cool idea, and they worked, but what ended up happening is all the games just added support for regular controllers, and that was just a better experience.

Steams built in controller customization features are worth it alone - for every controller. No digi pad makes them bad for retro games but I have others for that.