If you notice those evenly divide so any other number would mean that pixels might not be able to hit the right pixel on the LCD resulting in that fuzzy Windows look you see on the common other laptops.
Apple has had a thing for pixel perfect displays and this would be a way to break it in far too many ways.
Bob
I'm wondering if there is a way to set a custom DPI on higher resolutions on Mountain Lion?
When I say custom I mean anything but 72 or 144(retina mode?)

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic