At some point, you just have to respect and trust Apple to realize that they know what the hell they are doing.
They see a need for a 4in screen, they see the need for "pared down" essentials and super fast speed, and they produced a phone that's comparable to the 6s but at a minimum price.
I come across many high ranking businessmen in my job, and invariably, they all prefer the 4in form factor. They enjoy a portable phone that fits in their pant pockets and is slightly boxy and holds well in the hand. They are senior professional guys who want a phone just as a phone meanwhile they can do the heavy work later on their laptops or they have assistants who do that.
On the other end of the spectrum, I see lots of housewives with 5.5. They all have purses for their phones. Or they are shopping, doing their hair, picking up their kids with 5.5 in their hands.
Just from my personal observation, women prefer 5.5, more established men prefer 4, and the rest of the world go for the 4.7 or any model. Just my 2 cents.
Hey, what phone do you think Tim Cook carries?