why does it need to accommodate compatibility for archaic devices/software?
Because that's one of Windows' selling points. It has unusually good backwards compatibility for a mainstream operating system. Compare that to iOS, Android, MacOS, or Linux, where the infrastructure needed to run older binaries often doesn't exist in the first place.
Linux is a weird case, because thanks to Wine, it actually runs a lot of old games better than Windows, but this doesn't do anything to help compatibility with older Linux binaries.
Because that's one of Windows' selling points. It has unusually good backwards compatibility for a mainstream operating system. Compare that to iOS, Android, MacOS, or Linux, where the infrastructure needed to run older binaries often doesn't exist in the first place.
Linux is a weird case, because thanks to Wine, it actually runs a lot of old games better than Windows, but this doesn't do anything to help compatibility with older Linux binaries.