Followup question: why does the Windows installer defaults to creating only 1 partition, instead of creating something saner, separate system and user partition

Followup question: why does the Windows installer defaults to creating only 1 partition, instead of creating something saner, separate system and user partition, similar Linux installers for example? (This just came to my mind: quite possibly the Linux distro from MS also does the same) That way an operating system catastrophe wouldn't be almost always fatal...