* usable on pretty much any platform
* easy to distribute/update
* easily trustworthy/jailed (no need to install something that might access your data)
It makes me sad, but as far as I can see, there is no serious alternative for universal+jailed apps.
There are plenty of ways to distribute thick client apps that are usable from any client, easy to update, and which don’t have access to local resources, like Remote Desktop, VMware, Citrix, etc.
and ask your users to install those before being even able to use your app?
I haven't phrased my argument very neatly, but the point stands: anyone with an iphone/android/linux/… can easily use a web app, now, without any prerequisites. You don't have to bundle it or distribute it differently than with a webserver and it's a single codebase. That's not the case for any other tech that I'm aware, and it's a shame.
But it’s all about requirements. The benefits you describe are not universal benefits.
Mobile app stores, where users have to install apps, transact over a $1 trillion per year. Sometimes a native app provides a better experience.