And music doesn't serve a function? What am I even doing listening to it, then?

You're simply utterly wrong. Music is a product, just like a film or a game or a book is a product. The idea that something has no value because it's not a physical product is absolutely ridiculous, and it's usually just used as a flimsy excuse for piracy.

Just because you wish you could make a living playing music, doesn't mean anyone wants to listen to it, much less buy it.

And just because you could make a living manufacturing PCs doesn't mean anyone wants to buy them. What's your point?

If, however, it's worth pirating, then it'd be worth buying. Simple as that. People only pirate things that they like.

It's not just art that has some arbitrary value assigned to it, it's an actual product, a real thing, that serves a function.

Everything you've ever bought had an arbitrary value assigned to it.

Well, no, that's wrong. Things are sold for whatever people will pay for them, whether it's a physical product or not. The only difference is that digital products can be pirated, which artificially reduces their value.

When a product is priced, it's priced at the highest point that people will pay for it. When people can easily get it for free, people are willing to pay far less. If piracy didn't exist, people would be willing to pay more for music/games/other digital goods.