Don't listen to those who say "stop whining". It's a problem and it has to be addressed, people need to stop comparing Windows Phone with the PAST of other platforms unless they believe Windows Phone to be irrelevant or sub-par in the present, in which case you probably shouldn't talk anyway.
It makes a lot of sense, companies prioritise and Windows Phone is simply not on the radar for most. Microsoft can't force companies to create anything, and it's not a one-click procedure to go from Windows 8 app to Windows Phone 8 app. Simply sharing a similar design language (and even then, you'll notice that Windows & Windows Phone have very different layout guidelines) is but a small convenience in the grand scheme of development.