For example, if you run Google ads, you are paying a rate of anywhere from 66 cents to 5 dollars per click. If you don't like it, then you don't get to use Google's platform. That's a difficult think for a business to avoid though, so larger businesses are paying for at least the lower tiers of sponsored links.
Apple is, as part of the agreement to use their platform, expecting a cut of the links that users are clicking on that app developers are collecting. It all ties back to advertising and who is getting paid.
Unfortunately for Apple, they did poorly with their case with Epic Games. And have a burden that no other major tech company has to deal with. The law is being inconsistently applied, and I believe the way it is applied to Apple is unreasonable and confusing compared to how the rest of the tech industry is treated.