That's the status quo for historical reasons, but I don't think many see this as a desirable state of affairs.

Agree. But reverting this is really hard. Because it is crucial to .NET to play both fields right now for the next ten years :). Reworking Xamarin is not an option in a time when the race against Cordova, React Native, Node, Swift, Go and Python is fully ongoing. They are pragmatic here, how they should be.