Tying the size and density of your display to software needs-- especially points that are arbitrary to begin with (as they are based on the original iPhone) seems silly and outdated.
My first MPB was one of the "high resolution" ones that ran at 1680x1050 and I loved it. So when I first got my 15" retina MBP was miffed that now it felt like I was running a 1440x900, just with double (well, quadruple) pixel density. So I opened scaling preferences and set it so the retina screen would "emulate" a 1680x1050 display. It was terrible. Blurry and SLOW. Good lord it was slow. And impossible to do any design work on. I went back to normal 2x scale.
So sure, this kind of scaling has been available for a long time but the reality is most people don't scale their MPB retina displays to anything other than 2x.