To be fair to Javascript...
...end-users just don't get the concept of offline web apps.
At my work we're currently developing an iPhone app- at no small expensive, given that it requires hiring a contractor who knows Objective C. Thing is, absolutely everything we're doing with the app would be achievable using Javascript and HTML5's offline data storage capability.
But the end users don't get the idea of it- they are conditioned to believe that everything in 'Safari' is online and online only, and that if they want to do something offline, they go to the App Store.
It's a real shame, as the mobile space is where we're really going to see HTML5 adopted first.