When they first broke into the music selling market, the entire music market was open, and the fastest way to make money is to sell music. A decade later most people who want to buy music, middle aged people nostalgic for their teenage music with money to burn, etc etc have been tapped out. They still have to show similar revenue, and revenue growth to satisfy the Wall St bean counters. When you have over 75% market share already, maintaining revenue and growth becomes increasingly difficult. At this point they want all new music to go into the rental model with continued revenue potential.
Take a look at the Microsoft MsOffice market. It was selling perpetual licenses, and to maintain revenue growth it kept raising the prices. After reaching impossible for software prices like 500$ for a full office suite, 150$ for Excel+Word they could not sustain it anymore. Google stepped in with a low end Cloud-Office suite at 50$ a pop per year and made serious inroads into MsOffice monopoly. The first serious challenge, the first challenge to MsOffice franchise that got traction was GoogleDocs. We might laugh at the mickey mouse features of GoogleDocs compared to MsOffice, we might see OpenOffice and LibreOffice are far more serious implementations. But, on the ground, GoogleDocs had just two things going for it. Extremely good collaboration features and a tempting "it is just 50$, let us try it for a while" price. Now Microsoft is pitching OfficeLive365 as 50$ a year all you can eat buffet. It used to sell the entire suite for 50$ in the 1990s, student version perpetual license were 30$ as recently 2009. Now?
Almost all the software companies want to go into subscription model, software as service, rent not own, model. All the media companies too. Price blue-ray disc at 25$, but stream HD rental at 5$. Rent, not own. That is the way all media and software companies are evolving into.