That's a good question: Apple has argued in court that PWAs are a serviceable alternative to the app store.

So why aren't developers using them? Is Apple wrong? Are they not a serviceable alternative to the app store?

Android has better support than iOS, and Android's userbase spends less money on apps and is more often monetized through ads. So it's not the payment platform that causes developers to avoid PWAs, otherwise they'd be used all over the place on Android.

Android also has a semi-thriving community of Open Source applications through F-Droid that are privacy preserving and completely non-monetized. But installing apps through F-Droid is complicated. And F-Droid has zero user reviews. So it's clearly not the ease of delivery or advertisement that's causing those developers to ship native apps that need to be sideloaded through a complicated process that involves going into your phone settings and turning on sideloading instead of just shipping web apps.

So what's left? Well, invasive apps like Facebook/Twitter could ship as PWAs (with the caveat that their notification support would be worse). But they'd be giving up tracking ability by doing so. Web browsers are better secured than phones are. Facebook on iOS has an easier time tracking your behavior than Facebook in Safari does. Facebook on iOS could even at one point (and might still be able to, I can't find a source that this is patched) push custom code into web views of other articles through its iOS native app. So yeah, they're obviously interested in shipping an iOS app because (frankly) the Safari team is better at security than Apple's iOS developers are.

The only reason left that explains that behavior is the fact that PWAs on both Android and iOS are severely lacking in APIs that would enable anything other than shallow internet-connected services. They are not alternatives to the app store in their current state, no matter how much Apple pretends otherwise. Notification support on Android for PWAs is a joke, it's basically only usable for advertisements. And it's even worse on iOS. If you want to make an alarm app as a PWA, it is literally impossible to do that reliably. Want to make an RSS reader? I have no clue how that would be done as a PWA, I don't think it can be done without a web server handling the article fetching.

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And I'm sure you would say at this point that there are tons of apps that don't need this stuff and that really it's not about capabilities it's about payments and about what the users want and where they look for apps...

And I would just repeat your question back to you -- there are a ton of apps that are not monetizing through app store payments that aren't shipping PWAs. There are a ton of apps that are not looking for mass-market appeal that are not shipping PWAs. And Apple is arguing in court that they could. But they're not. They're not using PWAs on iOS or on Android. They're not shipping PWAs when they rely on advertising. They're not shipping PWAs when they would benefit tremendously from not needing to pay so many commissions to Apple. Even when they're Open Source and don't monetize at all, they're not shipping PWAs.

Why not? What do those developers know that Apple either doesn't know or is pretending not to know? There's no NewPipe for iOS shipping through Safari. Why is that?