I was writing a component for the media player foobar2000 to add MPRIS support and wanted to communicate with a small Linux daemon which would make the actual D-Bus calls. I figured Unix sockets would be a good way to do that, but Wine didn't support them.
I don't know of any applications that use Unix sockets on Windows; I'd guess the lack of popularity is due to both how recently support was added and the fact that named pipes already existed. Discord on Windows, for instance, uses named pipes for its IPC instead of Unix sockets (as on Linux and macOS).
One of the examples provided by Microsoft's documentation was communication between WSL2 and native Windows programs.