Apple doesn’t have the competitive pressure that I can take my broken iOS app and run it somewhere else as-is, or tell my customers to do that.
“It works in Chrome” (and previously IE) is a real issue and the browser that broke compatibility like that would have to be supported (potentially through the coercive power of its own market share - see the initial “any open source browser versus IE is a good thing” switching to “we need multiple browser engines, even if they’re all open source”) by the others or face irrelevance.
