I rather think, the main thing stopping PWA are that browsers still can not decide how to treat them. In some ways you can just do anything unrestricted and in other areas your PWA gets treated and limited like a random untrusted website, with no way to get needed rights. At least that was my experience last time I messed with it.
It is of course a problem to do it right, as prompts for confirmation just gets clicked away, but there should be a way to get real user consent for a proper app, that people trust.
But Apple for example wants to keep their app store under their control, so they surely won't provide an easy way to bypass the normal app store by giving developers a way to ship full apps just through the browser.