I absolutely agree, however the point I made is that the temptation of the market share means there will always be app developers willing to step in to replace

I absolutely agree, however the point I made is that the temptation of the market share means there will always be app developers willing to step in to replace any that withdraw from the market. If I'm an app developer, from a purely financial perspective, why would I forego a market of Apple's size, even with a 30% tariff? Sure, I may lobby for change, or even go to court to try to reduce that tariff. But while I'm doing that, I sure won't be leaving money on the table. And there's little chance I'll abandon that market in the interim, in order to maintain an ethical position.