Because Apple, a large part of the market, are actively fighting to stop it.
> No user is asking for web apps
And they shouldn't. They should not have to care if their app is a PWA or not. Developers need to care so they use the right tool for the job (native if they need the benefits offered by that, such as a performance boost or device wide access, PWA in most other cases where cross-platform concerns are more important than that) but the user shouldn't have to clamour for either.