Google Music has radio stations, as many (if not more) "precanned" playlists as Spotify, it's a higher quality music (as another user mentioned, double the bitrate), it has
more music (if it's on YouTube, it's on Google Music), it's Google so the UX is solid (and if it's not, you know it's continually getting worked on), and not to mention the integration it has with Android -- as a Google product, it gets first-class treatment by its devs (Google would never release a sub-par Android app for one of its top tier offerings).
I have $7/month to spend, and I want the best I can possibly get for that $7. Google Music is that product.