Well sure. But now you're parsing a file structure using arrow keys in a moving vehicle. The whole point of in-car is you've got a big screen and simplified navigation that allows you to flip between music and calls and navigation without endangering the lives of everyone around you. I can hit my files on my phone seven or eight different ways - DoubleTwist, Plex, Bluetooth, USB, whatever. But if you're going to put an interface in the car it should be better than kludging some bullshit MacMini-Winamp horror from the early 2000s.
And before it started to suck, Google Play Music gave you artist/album/genre/grouping/playlist whatever you wanted. Where it falls down is (A) it won't let you touch the screen more than six times before returning you to main (sometimes four - it's a dick) which means you can't even open up the album and return to the beginning - you have to rewind a song at a time and (B) it no longer lets you say "Okay Google, play Skinny Puppy" because it decided to lock that functionality out to paying customers. So now you have to reach for your phone, browse to Skinny Puppy, find an album and hit play. Because Google can't even lock you out right. I've bitched about the UI before. It's terrible. That wasn't my point, though - my point is that one of the world's most valuable companies, an organization that makes 95% of its revenue from advertising, which has my entire music collection as metadata, which has the world's entire music collection as metadata, which knows enough to know that Enigma and Lesiem and Balligomingo and Adiemus are related... ...thinks that what's going to convince me to pay for their service is interrupting me with L'il Jon.