I guess, most people who buy a steam deck already own a PC.

Would be the same for me. I’d get a steam deck to game on the go, but I already have (multiple) PCs. So why would I replace my PC with a Steam Deck?

It might be an use case for a student or other young person who is getting their first device, but then again I feel if you have only one device, a laptop is the more sensible, more versatile choice.

I’m pretty sure that for most people a steam deck or similar device is a secondary or tertiary device.