While that's true.... It wasn't until a few years ago that Apple owned a chip design company now did they? No reason for a company who builds consumer devices to own a Fab unless they own a chip design company right? I mean what would they do, buy someone else's designs and then FAB someone elses design? Might as well just let them design and build them entirely. However, now that they own the chip design, it only makes sense to move to the next phase and own a FAB. True?
For the same reason keeping them fabless for the other components, it makes sense to them to remain fabless for chips. Design themselves and let someone else build them, so they can negotiate for lower prices, make contracts for the quantities they need, and make sure they have them in time.
Running a fab is an unnecessary waste of energy. They won't be able to keep up with the demand they need, while substaining unnecessary costs in areas they are strangers to.