I think the percentage of iPhone users for who this would matter is very small. It's similar to how many people care about using a different browser than Safari on iOS (or Chrome on Google): in the US at least, those two browsers have ~95% market share.
Oh yeah? Then why don't they permit you to choose an App Store, a browser, a messenger, a blah blah blah...
And there are plenty of messaging apps on iOS.
App store, sure, they don't allow sideloading, but that's a different matter (and the number of users, not devs, who care about that is even smaller)
In all other countries, the "browsers" on the App Store are only skins on top of a crippled version of Safari.
You can set your browser to a Chrome UI wrapper around a Safari Webview. You can do this with any [browser] UI wrapper around a Safari Webview, as long as [browser] has received the relevant entitlement from Apple.[0]
Outside of the EU, all browser apps on iOS must run Safari's engine.[1]
[0]: https://developer.apple.com/documentation/Xcode/preparing-yo...
> Request the default browser entitlement by filling out the Default browser entitlement request form. If your request is accepted you get both the default browser entitlement, and the com.apple.developer.browser.app-installation entitlement. If you have the default browser entitlement, fill out this form to receive the app-installation entitlement for your browser app.
[1]: https://developer.apple.com/documentation/browserenginekit
> Important: To distribute an app that uses an alternative browser engine, you need to request the relevant entitlements for your developer account. For more information and to request the entitlements, see Using alternative browser engines in the European Union.
How do people imagine ad blockers get implemented? Why do they assume ad blockers will be supported by Apple, which once ran an ad network and runs an ad network in Apple News, forever?
If publishers wanted to support only ad-block-blocking browsers, that's their prerogative too! I don't either think Apple should get to decide that ads are protected if you appear in Apple News, but ads are not protected if you appear in Mobile Safari.
People opposing choice: it never ceases to surprise me.
But more than that, why are your arbitrary expectations any more important than their arbitrary requirements?