Where in mobile can you live-debug an application both visually and functionally like you can with Web Inspector? I mean literally you are coding and debugging your app at the same time. And with LiveReload you don't even leave your editor to see your code changes instantly.
Not to mention you are coding in JavaScript and CSS so the time it takes to iterate between various solutions is a fraction of the time of Objective C or Java. I think you have your first point backwards. There may not be an equivalent IDE, but we have a runtime inspector/editor baked into our runtime platform. You can't beat that.
- forcing users to upgrade their hardware to stay current
On Android you can update your default browser through the app store.
- app discoverability issues
Perhaps, but then again your app could just be rejected/removed at any time. Plus the whole 30% cut, time to release, limited sales options, etc. You're not in control of your app.