The move is yet another blow to publishers many of which are struggling to find revenue streams due to the increased use of ad blockers. With the prevalence of free apps, Apple's affiliate program likely wasn't a major revenue source but at 2.5% it's now pretty much negligible.
Starting on May 1st 2017, commissions for all app and in-app content will be reduced from 7% to 2.5% globally. All other content types (music, movies, books, and TV) will remain at the current 7% commission rate in all markets. We will also continue to pay affiliate commissions on Apple Music memberships so there are many ways to earn commissions with the program.
Apple has also announced an updated Affiliate Resources site and a new Getting Started Guide. You can check it out at the link below...