The average users sucks at managing bookmarks.
Telling a user that a feature is a webpage instead of an app means that they, in their glorious tech illiterate brain, think they have to memorize the url. They don't want to do that. They want to "have it" so they don't forget it. And having it is easier in the app mental model to them than in the bookmark one.
I know sufficient 40+ year olds who have the most absolute disgraceful phone desktops, filled with garbage. And yet, this is what they want. They want their bookmarkrs in the one place they'll check. And they want no folders.
Of course, Apple and Google will never do such a thing when their cut of app sales is ~$100bn globally.
And I did run into an issue where if the site allows me to install it as a PWA, Chrome will want to do that and won't want to bookmark a specific page on that site instead.
Also, maybe your point was that this could be done at the OS level rather than the browser, which is fair.
Don't forget that Google also has ChromeOS, it is Apple that isn't that keen on the Web.
On the other hand, thanks to devs and Electron garbage, the Web is actually ChromeOS nowadays.
Location and marketing matter. Otherwise we're in the Hitchhiker's Guide to the Galaxy where the aliens put Earth's demolition notice on the bottom of a cupboard in a cellar on a planet light years away from Earth.
Most people like apps because they're often better to use, unless you have accessibility requirements (and even then an app that makes sure accessibility is good might still be better than a website that makes sure accessibility is good).
I'd switch over to the 16-bit VB4 form version as soon as available.
The one example I know where they seem to have done a good job (at least in the beginning) is VScode, and even there it's not great. It's just not terrible. Put the same effort into a native app and it will be great.