You’re right, the end users don’t care. That’s not the point. The point is that forcing all iOS devices to use the WebKit rendering engine prevents competitors

You’re right, the end users don’t care. That’s not the point. The point is that forcing all iOS devices to use the WebKit rendering engine prevents competitors from closing off the web to Apple technology. E.g., Google has to make sure its mobile sites work with WebKit because they can’t just tell their iOS users to download Chrome to make it work. Any website that works for Chrome on iOS will also work for Safari because they share the WebKit browsing engine. If Google could release a version of Chrome on iOS that used its own browsing engine they could basically leave their critically popular websites broken on Safari and tell their users to download Chrome to fix it. Somewhat tangential, they could also get around the Apple App Store by leveraging the Chrome Web Store and extensions as an alternative.