Starting on October 1st, 2018, commissions for iOS and Mac apps and in-app content will be removed from the program.
I never reviewed app because of the monetary return, I did it for the fun of it. However I know many sites that this is a huge revenue for them, and the few £ income I made did help.
This is a baffling move by Apple, and one that will upset a lot of people. I have no idea why they would do such a thing, but I guess they think their curation on both app stores is better.