Largely because I've yet to use a streaming service that handles intermittent connectivity well enough
If you have an Android phone: Google Play All Access.
You can offline content to your phone as if you own the music, but you get full access to their complete library. It's pretty brilliant, IMO.
Edit: though that doesn't help you if you're looking for a radio-like service... I tend to listen to albums at a time, and discover artists through third party services (e.g., Rate Your Music) that then drive me to sample stuff on Play. So it works well for me.
Once I've decided I like something, I tend to want to actually own it.. Play's opaqueness when it comes to telling me what's DRMd and what isn't (may very well have changed - I haven't bothered checking in a very long time, and to be honest I don't know whether they've ever had DRMd music at all, because their lack of transparency with respect to video content and ebooks mean I never bothered even looking at their music section) has kept me away from using it at all for content.
Google Play's radio feature has been amazing in my experience, and way better than Spotify's. Especially for stuff which is a little bit out of the mainstream, the selection-quality is so high that I wouldn't be surprised if they were using some of their Google suggestion-fu to generate it from what tracks users have played together in the past.
Oh yeah, my only point is offlining/intermittent connectivity and the radio features are kind of at odds with one another... but that's not unique to Google in any way.
If you have an Android phone: Google Play All Access.
You can offline content to your phone as if you own the music, but you get full access to their complete library. It's pretty brilliant, IMO.
Edit: though that doesn't help you if you're looking for a radio-like service... I tend to listen to albums at a time, and discover artists through third party services (e.g., Rate Your Music) that then drive me to sample stuff on Play. So it works well for me.