Even the best websites don't feel as smooth as native UI elements, and somehow browser compatibility is still a very common issue. Signing in with Google and using gpay for checkout is kind of close, but each website has different design elements complicating the experience while giving up the same amount of your personal data as if using an everything app.

Among other things said, you lose access to push notifications / scheduling which a lot of apps are reliant on.

You could have those come in an email instead, but now it's not personalized to the app or notification type, and if you're like me, I actually disable alerts on my gmail because most of the things in there aren't important and it was too disruptive.

Web browsers don't integrate to a single account and payment system, nor do they preemptively load entire websites before you start browsing. So you're always waiting for actions to complete or for images to load which feels slower. Mobile websites also tend to be very bloated slowing things down further than if the same functions were done natively in an app. There's also no consistency between websites so you never know when something will/won't work nor how far away you are from checkout. And then to top it all off there's browser compatibility, which is typically pretty poor for anything that isn't Chrome/Safari.

If a web browsers could really do the same thing all these companies wouldn't feel the need to make their own device specific apps.