Retina is a great example of how Apple operates in general. They care about outcomes, not spec sheets. Sure, they'll take the time to spec dunk when the opportunity presents itself. It's just rarely the reason they do something, whereas Dell/HP/whatever want to say "4K SCREEN OMG" on the box regardless of whether that actually leads to a better experience.

Apple realizes there's diminishing returns in upping the resolution beyond what your eyes can see. So they hit Retina, and then move on to focus on color accuracy, brightness, and contrast.

They do this throughout their product stack. Only as much RAM as their phones actually need, because RAM is both costly in terms of BOM and also consumes battery life.

Using fewer Megapixels than competing phones because it's about the quality, not quantity, when other manufacturers trip over themselves to have the most Megapixels.