It's plummeting because it's run by in outdated ways by companies that haven't adapted to new technology. A forward-thinking company that embraces technology would have some advantages.
The very idea of a 'record label' is a relic of the 20th Century, when all recorded music was distributed on heavy physical artifacts.
Also, Apple's iRadio is probably not taking off as well as they'd like and Beats Music already has a better feature set.
Music is now competing for attention with apps, push notifications, emails, SMS, etc. Listening to recorded music was at one time something to do in and of itself. Today it's something that's done almost exclusively in the background.