I suspect one reason is that it doesn't make sense for everything in a namespace to actually be a file. For example, making something like Control Panel or My N

I suspect one reason is that it doesn't make sense for everything in a namespace to actually be a file. For example, making something like Control Panel or My Network namespaces is a cute way to make them browsable in Explorer and similar tools (to find a network host, etc) but making those entries files would be a kind of pointless thing to do - almost every assumption you might make about files wouldn't hold for any of those entries. Of course, as you point out the right abstraction in many cases is an abstract filesystem, and for whatever reason pluggable filesystems aren't really a Windows Thing (though I think they may have been added recently for features like OneDrive and lazy git checkouts). The existence of shell namespace extensions probably stopped that valuable feature from getting put in...