It was quite a shock to me when I actually took some time to see how Spotify looked and played on a smart phone when using the free service. It's awful.
First of all you can't play an album or playlist in order. The only option is to shuffle the tracks. The individual songs are grayed out so you can't tap on a specific song you want to hear.
The music is then interrupted by commercials which totally ruins the experience of listening to an album. And it's a bit jarring if you're deep into the experience of an album. Really, Dark Side Of The Moon with ads interspersed is dreadful.
Then there's the lesser quality of sound. The free service stream is noticeably worse.
Finally, you can't download songs onto your phone for off-line listening with the free version. This is not only useful when you're out in the boonies with now internet but saves you from eating up monthly data usage. Being able to create a playlist of 10 albums or so that I can listen to throughout the week in my car without worry of hitting my data cap is gratifying.
The $10 monthly subscription seems a pittance after finding out the realities of the inferior free Spotify.