Earlier quoted context omitted.
Good grief, what the heck does Spotify do with 3000+ employees?
Definitely NOT making a mobile app with decent UI. Jokes aside, having to negotiate with tons of artists and their labels/managers, I imagine their legal/business department is significantly bigger than that of most tech startups.
AC/DC, Led Zeppelin, the Beatles and Taylor Swift come to mind, but there are very few artists who have a say in whether or not their catalog can or can not be streamed. Those artists made wise business decisions at some point and/or were able to throw their weight around. Here are some notable hold outs as of 2016 anyway:
https://consequenceofsound.net/2016/02/which-artists-are-sti...
Using Pink Floyd as an example, the decision was there's and not their record label EMI:
http://www.rollingstone.com/music/news/pink-floyd-catalog-ar...