Web developers like them. That’s it, and their PWA advocacy completely disregards what a privacy and security nightmare they can be without proper safeguards, because this little device I carry around in my pocket is 1) always with me and 2) stores a lot of information about me 3) has a full sensory array installed within it.
Every new feature browsers add for better hardware access gets immediately disabled on any system I manage: cameras, mics, USB access, sensors, location, notifications, local storage, the whole works because the alternative is letting every website access those or getting spammed with access requests on every site I visit and the more crap that is added, the longer it takes me every time I setup a new browser install from scratch. Why disable them at all? Because 99% of these new features are primarily used to build a better supercookie to track and profile people without their consent. The actual marketable reasons are a secondary use at best.
So if it’s not on Apple’s priority list to build out whatever they need to support and allow other browsers to support PWAs in a secure and privacy conscious manner, good for them. Web developers who want to circumvent Apple’s fees entirely don’t need to be anywhere near their top priority and can wait. For Apple: users come before developers, and App developers before web developers.