People buy it to use like console
- Xbox is basically using Windows Core + the xbox shell and runs the games in virtual machines.
- The PS4/5 use FreeBSD with their shell and libraries on top.
- The Steam Desk ships Linux and a shell on top of it (Steam Big Picture + Proton).
modern consoles are just PCs using PC OSs with custom UIs that fit the control scheme.
The only one that I could think of that's heavily modified is the Switch.
However, since the release of those 2, seems like Microsoft and Sony use an off the shelf OS + their Shell and APIs (graphics, networking, matchmaking ...etc), which makes sense, especially for Microsoft, as they already develop a very capable x86 kernel, so why not use it.
Afaik, with the introduction of the Xbox one, they used the Windows 8 Core as part of their "One OS" strategy to unify all of their devices on the same platform/OS (eg. consoles, mobile, AR/RV, PCs ...etc).
The current version of the Xbox OS is based on Windows 11 [0].
Ofc, it's not exactly the same as Windows, but, it's largely based on it, at least as far as we know.
[0]: https://en.wikipedia.org/wiki/Xbox_system_software
EDIT: Added the wikipedia link. It's the only source I could access from my work's network, but it show's the OS progression since the the first generation Xbox