I'll vote for the distinction being rf distribution vs. other means.
If it's only in a wire, cable, or fiber optic, it's an audio service that's still looking for the right name.
I will not diminsh or demean the value, enjoyment, fun, usefulness of data-distributed audio.
But there's just nothing at all of the magic of radio in such methods. At least for me.
Radio engineering school was the most fun time in my life, and part of me has never left radio engineering school.
Building so many receivers and transmitters over years and striving for the utmost in AM fidelity
makes it hard for me see streaming audio as much more than a glorified one-way telephone call.
Again, not to diminsh the value, I longed for such a service 30 years ago.
I'll echo 4CX1000A's points and add the "always up" nature of the laws of physics as a major difference and advantage
over human-devised networks.
If/When data access to the network is acknowledged as a basic human right, and as free as the ether,
then it will be an equivalent to radio. This will require a lot more bandwidth, pipe, AND distribution points
than anyone wants to pay for now.
The magic of self-propogation and immediacy still won't be there.
For me, that is the heart OF radio; content and the business aspects are just "necessary" evils.