It is odd to go after Beats and not Spotify and its insanely larger user base. But Spotify is apparently bleeding money having to pay 70% of its income to royalties, and is said to have lost $200mil over its lifetime, where as Beats is a relatively clean slate. Beats is also a domestic brand as opposed to Spotify being Swedish which may result in a cleaner hassle free integration with iTunes and its infrastructure and licensing agreements.
Ultimately it is Apple catching up to Google who added a subscription service to Play Music in May last year - being the only provider to offer subscription streaming, an online music store and cloud storage for you own existing library, in a single hub. I started using it recently myself and its brilliant.
Don't rate the headphones - though it does fit with Apple's high priced fashion accessory modus operandi - but I'd assume if Apple wanted one side of the business they have to take the other.