Birds sing for a lot of reasons. That we know of, they sing to mark territory, to warn of intruders, to attract a mate, and very probably for the sheer joy of it. The odds are high, awfully high, though, that never once has a bird song because it had a recording contract, a big advance, and a tour. If someone were to go out in the woods and record some birdsong, we'd laugh at them if they tried to claim that they owned the song, and doubly so if they tried to stop someone else from recording those same songs.
Yet, for some reason, we tolerate exactly that behavior from record companies. Curious, isn't it? I'm sure that some of the singers will tell you that they wouldn't sing if it weren't for the money...and for every one who said that, there'd be ten who'd say it was "for the chicks." (Or whatever floats their boat.) My bud back in high school who was in a garage band - come on, even though their Robert Plant was half-credible, there was no way they were playing those instruments because they had a recording contract.
Being in a band actually works very nicely as a fitness display. Not every human endeavor is about who is stronger or faster or meaner. We're social animals, and there's nothing like a good display of social behavior to show off to the opposite sex what a great catch we are. A band of musicians, well, first off they have to have enough social skills to actually be a band. Oh, and they have to play music, and if you think that's easy, you've never tried. And then there's that whole business about being in key, and being in the same key as the other musicians, and all of that tempo stuff, and pretty soon you're talking some pretty significant brainpower just for three or four guys and gals to actually play music that someone else has composed. Once they've mastered those skills, then it's on to learning the next song, then all of the organizational skills in putting on a show, getting an audience to show up, and it may even be that as they sing they're going to dance to the music, and now you're showing not just the fine coordination to play an instrument, but general health and athleticism.
So, really, the reason the band gets some good nookie? It's because they're earning it. Yeah, if it's a typical fraternity party, the frat boys have gotten good and stoked while the sorority girls have gotten stoked up, so the only eligibles left upright are the members of the band, but still, the band would not look at all attractive if they weren't showing it.
Now, this doesn't mean that the entire world's body of art is worth nothing as long as the artists got some. However, come one, $150,000 a song to some bunch of suits who had nothing to do with the process except that they provided a microphone at the right time and place? That's as ridiculous as the guy out in the woods listening to the birdies calling him cheap, cheap, cheap.