Not all gamers have a computer entirely dedicated to that purpose. Even among those that do, it's not uncommon to also play games or run Steam on another machine.

I have it installed on a non-gaming laptop. There are lots of lightweight games that I might play when traveling.

I still have Steam installed on the laptop that was long ago replaced as my gaming computer but which is occasionally used for other purposes, because I have no particular reason to remove it.

How is that relevant? The question was whether the resolution figure in the survey is hardware resolution or software settings, and it's the former.

It's actually probably reporting the software-configured resolution, not the hardware capability. The important distinction is whether it's a system-wide resolution setting or a game-specific setting that may not apply to browser contexts (except for the ones used by Steam itself).

What makes you think that it’s more likely reporting a software-configured resolution? It is after all a hardware survey, and focused on what user hardware supports.

It's vastly simpler, and more useful, for Steam to detect the current resolution. Trying to detect the maximum supported resolution is non-trivial, especially when there are devices that will accept a 4k signal despite having fewer pixels.