Actually Lumia 1020 showed us why .. (the pixel chase in cam phones).
Because lens design is restricted in a phone cam(by size) .. they can't really create zoom lenses easily or effectively.
Lumia's response to this is to crop digitally!
45Mp down to 8Mp is quite a massive crop ratio .. looks like a zoom action keeps the don't-really-care set happy as they get all that they want.
Makes sense to me(from a make zillions of dollars by selling to the masses perspective .. not from a I-want-the-best-image-quality gearheaded point of view!)