I think the problem is that Marco sees Instapaper users as his customers. I sympathize with this, but I think iOS is an assertion by Apple that App Store custom

I think the problem is that Marco sees Instapaper users as his customers. I sympathize with this, but I think iOS is an assertion by Apple that App Store customers are Apple customers. App Store Developers are providing a service to Apple's customers. But everything that happens must point back to Apple's servers, not their own. In the same way Apple doesn't want every developer operating their own independent payment system, they also don't want developers operating their own cloud storage services. If Apple holds the data they can guarantee its security. They likely see these problems as temporary, until developers and customers learn to adjust to the fact that iOS data is controlled by the iCloud service.