Why can't we just get rid of most native apps and app store duopolies? Or at least complement them with good web apps, that work offline, use service workers, small sized and so on?
How does web indexing help the end user?
Sharing what?
How do you imagine that a cached webpage is more private than a locally running compiled app?
You can't install an app without accepting all permission, contact info, sms, and so on. Facebook is much more privacy agressive on native than on the web.
If you don't care about high quality of UI, then sure.
(Also, it seems from my perspective, that clients with money here care most about being on iPhone, and service workers there are not yet ready for primetime. Its only been available for 7-8 weeks, and it's got some warts - only 50MB of storage, your cache and persistent storage may vanish after only a few weeks, and no push notifications - which is the showstopper where I am...)