As for the web being the de facto solution for light tasks, I'm not sure I agree there either, at least with the web's present resource consumption problems. There's no reason, for instance, for a word processor that barely matches modern WordPad or Word 95 in terms of features to be as heavy as it is (Google Docs).
If web apps were being approached from the angle of resource consciousness and taking advantage of platform strengths, I might have a different opinion, but that's not what anybody developing web apps wants.
We already see this (and solve for this) on desktop and platforms with a lot of variance in capability like Android. Just because people out there run 2.3 Android doesn't mean my 7.1 apps are going to be any less quality, even if they still work on the least-capable platform's featureset.
The obvious solution to this is to exclude or disable features from devices that can't handle them, which is also possible and encouraged on the web (with some decent precision through identification and fingerprinting provided by a myriad of things like service workers). Your banking site probably works in IE8 (barely), but that doesn't mean your up-to-date Chrome/Safari/whatever is going to be a worse experience.
>If web apps were being approached from the angle of resource consciousness and taking advantage of platform strengths, I might have a different opinion, but that's not what anybody developing web apps wants.
Web apps are focused on optimizing _different_ resources than native apps, that's all. Google Drive, for example, offers me an experience with no local installation cost in storage, virtually unlimited storage space for files, ancillary services like backups/authentication/sharing/etc handled for "free", native-like responsiveness while working offline, a low barrier-to-entry (unlike downloading/installing an app), a smoother experience across multiple devices, etc etc. These are all qualities that a web experience does better, and I think these are all qualities that people (myself included) value over the separate benefits of traditional native apps.