And you're almost always better off making that change yourself.
Big publishers have their own payment processing pipelines. Apple's is just extra overhead. Smaller publishers still (IMHO) can see a lot of benefit from Apple's 30% cut. It's those large publishers who are most likely to challenge your rules in court or lobby against you.
If the very largest publishers were paying 10% as a Preferred Partner instead of 30%, they would be a lot less willing to challenge the status quo when they might lose that privilege.
We've already have ridiculous workarounds for Apple's policies here like how you can bypass it to buy directly from Amazon through the app for physical goods. The carve out for digital goods is and was always a tortured post facto justification.
Where once the 30% cut funded the App Store (when it was small). It's clearly transitioned to being a massive profit center and Apple executives couldn't see past the short term revenue to see the writing on the wall. Woops.