Its more about the convenience of having pretty much any song you could possibly want on your phone. Just take it out, search for a song in Apple Music that you want on a whim, and add it to your library. Or just stream it. Sometimes I'm just listening to music while web browsing on my phone and I'll think of a song/album that I want to hear and I'll just search for it, and add it directly to my library. If I didn't have Apple Music I would have to get up, go to my laptop, download the song/album and connect my phone to my laptop to sync it with my library. You don't see how much more convenient it is to have Apple Music?