Well, at heart it’s a more fundamental issue with the nature of publishers of creative works in general (music, books, movies, games): most don’t make money, but if you’re a publisher, you have to damn well make sure your expenses are being covered, or you won’t be a publisher for long. There’s a big structure with fixed costs that needs to be maintained to get the artists’ work out there. So publisher’s needs go first (and that means taking a bit extra to cover the artists that didn’t bring in enough money to pay for expenditures on their behalf, plus some profit), and whatever is left over in theory goes to the artist.
Unfortunately that structure allows for all manner of parasites and financial shenanigans and over-paying of certain people (management) on the publisher side, so the artist getting getting a fair share isn’t remotely a given. But even when it’s working in a reasonable manner, as fair as it can be to the artist, the fact that there’s a lot of money at play doesn’t mean the artist gets much of it.
