Re: But why?
The iTunes radio is not an internet radio but rather Apple's attempt to push aside Pandora. I for one want to listen to my favorite Christian station (KLOVE), but the app isn't what I was expecting. You cannot select an internet streaming provider and listen. Instead you select your genre and Apple feeds you songs out of their iTunes catalog, which you can then conveniently buy. So you will need a third party internet radio streaming client app.
Also the Apple "intuitive" navigation isn't happening for me with this new release. I have the same nausea that I felt when I encountered the ribbon in Office.