^ Jobs’ thinking was that the iPhone should be able to be manipulated with a tool you already literally have on hand. In other words, your hand.
If the screen becomes too large then the average thumb will not be able to reach all the way across.
Perhaps It’s my design education speaking, but it it desirable to be able to manipulate any device, smartphone to door lock with as few hands as possible.
Also, Apple, like another company I admire greatly, Honda, isn’t slow to jump on certain concepts because they are unable to, but because the are conservatively waiting to see if some technologies are mere trends. Honda went so far as to, instead of creating their own SUVs had existing Isuzu products sold badged as Hondas (The Passport) and Acuras (the SLX). Once it sadly seemed as though the pointless SUV trend was here to stay they resigned themselves to develop their own.
Soichiro Honda likely turned in his grave at the idea of his name being placed on another company’s products, But something had to be done.
Honda, like Apple innovate on their own terms.
Note: If you have a Honda or Acura badged Isuzu, take it to an Isuzu specialist. Honda techs hate working on them.