If I'm at the app's entry in the Store (similar to the navigation I need to do to first visit a web app), I can install an iOS app in 1 click of the Get/Purchase button (plus the thumb touching for authorizing the sale). I'm pretty sure it's the same in Android.
Even better, with the native app I don't have to create an account, re-enter my details and suffer all the BS that I have with web based commercial services. Plus, Apple/Google already have my credit card details.
I also don't have to suffer a lowest common denominator platform, or wait for the the web standards AND the vendor to have new native feature access finally trickle to the phone's JS engine.
>Deciding to install an app is a lot harder than deciding to use a web app.
Committing to a web app (for a user), and monetizing it (for the software author), is much harder -- especially on mobile.