The track pads are phenomenal for any game that doesn't have great built in controller support. I use them for mouse input on games like FTL, and they are much more accurate for aiming in FPS games than emulating a mouse on a stick. I also use them as radial menus for expanded controls on games like Elite Dangerous that really need more buttons than a controller has.

I agree with your point in general, and SteamOS was the main thing that pushed me towards steam deck over other handhelds with better specs. Now that I've used it though, it would be hard to give up the trackpads if the other options dont have the same quality. My hope is that 3rd party devices will basically mirror the steam controller setup, since the SteamOS controller mapping and provided layouts are a huge part of why so many games work on the platform even without official controller support. It's not just the hardware or the software but how well they work together.