Imagine you are making $$$ from your app or site.

One day you get an email "we'll remove your app because we found out you didn't pay us enough protection money. There is no appeal, we are a trillion dollar company, whatcha gonna do?".

You instantly lose half of your income in the best case, 100% in the worst case. There is no alternative app store for iPhones outside of the EU.

DMA is supposed to fix this, but it's only for the EU, and look at how Apple tried to spite the EU with their "compliance".