Why not create a new URL handler that takes an app-specific user ID that redirects to the correct profile page only if the logged-in user has permission to view

Why not create a new URL handler that takes an app-specific user ID that redirects to the correct profile page only if the logged-in user has permission to view the page? That way, you would normally only be able to see what the world would see; but if you try to view your or your friend's profile, it's fluid?