Think about it this way.....
The idea that the lock screen wasn't dealing with all notifications in kit Kat and just showing you the music is actually a limitation of the kit Kat OS. Now, background art and a card with controls at the top make more sense given that all notifications are showing on the lock screen. To me, kit Kat did a bad job of handling notifications.
I think about it in the way that my iPhone 4s did both and I'd rather have my music controls than anything. Plus, I had SMS notifications and just swiped across to see them.