True, but Steam deck lets you boot into the Linux desktop environment of the os and you can do whatever you want with it. I have installed games and emulators outside of steam on mine pretty easily.
You could probably even put a different Linux OS on it entirely if you wanted to.
That control over the platform was the biggest selling point for me. More control even than the windows based handhelds.
You could get one of those Bluetooth keyboard/ trackpad combos and a case with a kickstand for desktop use. Small screen but usable. I personally wouldn't replace a laptop with it, but if you didn't have a laptop it could be useful to buy one device that does handheld gaming and other stuff too instead of buying two devices