IMO, Non expandable storage works for apple so well because of this 2 reason:
1. Customer have no choice, if they want iOS they have to pick iPhone.
2. Their applications are sandboxed, data cannot pass freely between apps. (can have restricted access thou) - having the ability to expand storage with this design can be 'confusing', because you need to take into account what to do if the user pull out his sd card when he exceeded his own local storage? - Pretty much like the move2sd for android.
For android, expandable storage works so well because of :
1. All applications share the same local data, it is reasonable to have expansion, much like a PC.
2. sd card performance is on par with internal storage nowadays, the slight drop means nothing, you can listen to music.. edit doc.. video all fine. Gone are the days of android 2.3 512mb move2d phones.
Rather then thinking of "It is enough for most ppl, do not need to include", they should be thinking "It is enough for most ppl, include anyways."