One explanation could be that Apple doesn't want an "electron situation," where every app comes with it's own fully-loaded web browser, is a memory and CPU hog, and a security risk if the app is out of date. Like is currently happening on PCs.

With WebKit, its update once, secure all apps everywhere.

I'm curious if FirefoxOS had gone differently if Apple and others would've considered supporting a native-web approach for apps. (Albeit also tied to only one or a few blessed HTML and JS engines.)

That was the Apple party line when the iPhone was first released – the only Apple-blessed way to build iPhone applications was to build mobile-friendly web applications. There was a backlash – everybody complained and demanded native applications; the App Store was opened the year after.

https://9to5mac.com/2011/10/21/jobs-original-vision-for-the-...

IIRC FirefoxOS did it differently. Apps were local bundles of web tech. Not only pinned links to open a browser.

Apple was in critically bad place when windows dominated with Internet Explorer, and Adobe with its apps. These two companies dictated where the users would be, and Apple had to beg them to play nice.

The iPhone was a whole new platform where Apple had 100% power on where it could go; opening the door to third party browsers to bring their domination to the platform from the start must have been seen as suicidal.

Another explanation, less popular, is that Apple restricting to WebKit actually helps foster browser competition at the moment.

Let me explain. Right now it's WebKit vs Blink (Chrome and all Chromium-based Browsers, including Brave, Vivaldi, Opera, Edge, etc.). If Blink were to be allowed on iPhones... you'd see Chrome become even more dominant. Firefox is dying on PC, has less than 1% mobile share, and is no competition in this case.

Requiring WebKit is what prevents an even greater Chrome monoculture.

It is totally about preventing alternatives to the App Store.

That's the rule, but you have to wonder why. They don't get more money just because Google can't spend their own development resources on targeting and validating Blink/V8 for iOS.

90% of the revenue is games. Mobile Chrome would only need to support idiosyncratic Unity and Unreal web targets for a significant chunk of that revenue.