> Why would they have customers in the first place if all they offer is reruns

You can ask the same question for cable TV, but it's not dead. Netflix also started as purely "reruns" and was still quite popular.

> Creating and streaming audio is not a comparable business to creating and streaming video, due to the vastly different sums of money, and hence risk, involved.

If anything that extra risk should make studios more shy of investing in new content vs just serving up old hits. It's noticeable that film leans way more heavily on franchises and remakes already, which agrees with this hypothesis?

> That means there is less money available for new audio creators. And this holds true for all rent seeking. If it weren’t for excessive copyright, there could be much more variety in audio streaming.

You assume this, but I really don't think it's true! Most people don't seek out new music; their tastes are set in their youths and then they happily listen to the same music for the rest of their lives. The choice is to make them pay to listen, generating at least some stream of royalties, or let them listen for free, in which case they will be happy to.