Congrats to them, but I don’t think I’ll ever understand renting music. I can understand Netflix’s success because movie content is much less replayable and more expensive, but music is relatively cheap to own your own collection. I love music, but I don’t understand the appeal of Spotify and Pandora—I’d rather take the cost of subscription and build out my library over time.
Think of it as a subscription to a larger library than you'll ever be able to amass yourself.
Sure, you'll collect all of your favorite music, but what if you want to branch out a little? What if you want recommendations that are tailored for you, based on your music taste?
For me, one of the main services Spotify provides is access to occasional music, stuff that I wouldn't bother to collect, but is nice to have on hand, either for parties or just curiosity. The other main service is their recommendation engine, which reliably presents me with interesting bands and albums that I didn't know about, but fit very well with my tastes.
I consider $10/month a bargain for those services.
(I still keep an offline collection of my absolute very favorite albums, of course)