Question for you, as someone who has developed a mobile app:
How much harder is it to optimize a mobile version of the webpage vs writing an app from scratch and getting it approved for App Store release?
Mobile developer here who has done hybrid apps, Android apps, iOS apps, web apps, etc.
Web apps do not get the native scrolling mechanism, so scrolling feels very funky in web apps. Web app developers write their own inertial scrolling mechanisms to try to deal with it, but web apps always feel wrong as a result.
You also don't get access to a lot of native functions. No barcode scanning. No access to the user's preloaded Facebook account (with authorization, of course.)
There is another problem in that, especially on Android, web technologies are just badly supported. It's getting better in more recent versions of Android where Chrome is actually the engine used end to end by everyone, but earlier versions still on Google's old ass version of WebKit blew chunks.
Loading can be a problem as well. Real apps by definition cache a certain amount of code and resources on the device. A web page has to fetch all resources from start to finish. So while a real app has it's loading UI cached on device, and can display it right away when the user taps a link, a web page has to go fetch a UI over the network to display a loading UI for the operation the web app is about to do over the network. Gross.
The other really messy thing is a real app is pretty easily able to figure out what kind of device it's on and render content accordingly. Web apps can kind of guess what type of display/device they are running on, but again, it can be messy. Especially with new things coming like Adaptive UI/multi windowing coming on iOS where your window or screen size may have no real connection to what kind of device you're running on. Web pages at this point basically assuming they're always rendering full screen on mobile, and do their layout computations based on that, but that looks like it will change on future iOS and Android devices.
You also have a problem with native widgets. If I code a real iOS app, if I run it on iOS 6, it looks like iOS 6. If I run it on iOS 7, it looks like iOS 7. I don't have to create new assets, the app automatically ingests the correct look from the widget set built into the OS. With a web page, I get the "joy" of building my widget set from scratch, and trying to make it at least resemble the system UI widgets the user has been trained to use. And better yet, if I make my web app look like an iOS app, I suddenly have a bunch of Android users unhappy my web app looks like an Android app.
Finally, web apps don't offer any way to be embedded as extensions on iOS, or activities on Android. You can kind of fake it with some really really ugly URL handling handshaking, but this is really problem prone.
TL; DR: Mobile web frameworks/browsers are still immature, and don't offer basically mobile specific functionality that's needed to do apps well. It's not a problem of it being hard to do a web app just as good as a native app, it's a problem of it being impossible because the feature sets just aren't there.