Well, spotify works on android, windows phone, iphone, and has browser-based client too.
They also provide sdk for subscribers so you can write your own player if you want.
Itunes, it's probably one of the worst applications I've used. Platform support? One, more perhaps later..
Sdk so you can write your owwn app? Yeah no.
From technical standpoint, apple is hopelessly late to the game.
They could compete by undercutting pricing but this is apple we're talking about, profit before anything else.
I think I'll keep my spotify subscription for now.