One way they would be pertinent would be if the royalty rates are the reason the business is unsustainable, then the question arises if the goal is to have other folks hear the music or not.
So there is a cost to deliver songs (servers, bandwidth, devops, engineering) which is analogous to the old radio days of the engineer, power, transmitter, tower maintenance, etc. And there is the revenue from advertising and/or subscriptions. And there is the royalty rate.
If you are managing your on-going costs to a minimum, your ability to sell advertising/subscriptions is a market thing (people will or won't buy the service based on the perceived value to them) and then your royalties come out of that.
How would make an argument that royalty rates aren't pertinent?
Well, I don't really believe in royalties to begin with, but if you're going to have them...
I think royalties should be set in a way that maximizes what I'd call the versatility of utility. If royalty costs are far beyond the actual infrastructure or service costs, it seems as though entire industries and uses of content cease to exist.
It also seems pretty clear that huge differences between prices and real world costs are what lead to extensive piracy - people develop a perception of being cheated when you try to charge $25 for an e-book or album download. On the other hand most consumers seem to feel fine about paying $1 or $5 for a song/album/e-book.
You could argue that 'oh, the creator should have the right to control what they make as much as they want and charge whatever they feel like,' but it seems pretty clear that given free reign, copyright holders feel entitled and abuse copyright in ways that entirely undermine the whole system.
I'd say that if you believe in copyright there's a legitimate interest in restraining royalties to reasonable amounts so as reinforce the legitimacy of the whole system. After all, the perceptions of gouging and rights abuses create large masses of people like me who no longer believe in copyright as a whole to any great extent.
Ensuring the liberalization of restraints and apparent reasonableness of exercised privileges allowed creators seems key to creating a copyright institution that can survive and appear legitimate in the long run.
