Hi! Atlantic Records songwriter and previous Universal Motown artist here. Net worth and actual money paid to the artist are two very different things. Net worth calculates what is brought in as a whole but it doesn't account for what happens after that money comes in. There's so many factors that come into play here but I'll tackle the big few. First of all, let's talk about "recouping". Labels are essentially banks that give artists they believe in a giant loan. You then use this giant loan to pay for producers, writers, mixing and mastering as well as a million other things. But after you release your record, you have to pay back those loans through percentages of your profits. This is called "recouping". Now, it used to be that labels only took out this percentage from your album/single sales. But since the internet started semi-crippling the music industry, the labels have adapted 360 deals, which take percentages out of EVERYTHING. Merch, touring, special appearances, you name it. After you've paid back this loan the label takes a smaller portion of your sales but still a portion. On to the second part, the team. Kanye West has a manager, a publicist, a lawyer, a booking agent as well as some other stuff only superstars have, but all of them take a percentage of his profits AFTER the labels taken their percentage. The standard rate for just a manager(if you have no leverage) is about 20%. Now stack even more percentages on that for the rest of the team plus the (hypothetical) 50% taken out by the label initially and suddenly Kanye's made little to no money off of that 130 million. This is hypothetical Kanye though, he became an artist before 360 deals came to fruition so he's probably better off than most artists. Also, labels don't take cuts of outside things like clothing lines, shoes, etc.

TL;DR: Labels as well as Kanye's team take large percentages out of the initial profits before they even reach Kanye. So when streaming services start diminishing those initial profits even more, artists get pissed.