Developers can now take advantage of iOS 9’s app-thinning feature, which cuts down on the initial size of applications on your iPhone and iPad to maximize storage space, and device-specific “thinned” apps will now be made available to consumers using iOS 9.0.2 or above.
App thinning (or “app slicing”) is particularly useful for owners of 16GB iOS devices, a capacity that’s nowadays far too small for many people. With apps taking up a smaller footprint, those same iPhone and iPad users may begin recovering precious storage — but only if the apps they download take advantage of thinning.
As to per why Apple still sells 16GB devices, the company’s Senior Vice-President Phil Schiller tried to argue that cloud services have lessened the need for copious amounts of built-in flash storage. “The belief is more and more as we use iCloud services for documents and our photos and videos and music, that perhaps the most price-conscious customers are able to live in an environment where they don’t need gobs of local storage because these services are lightening the load.”