Apple and Microsoft worked on arbitrary resolution independence for years. It's nearly impossible to make it work right because things look blurry unless you redo everything as vector graphics and even that isn't perfect. [1] (Appropriate hardware wasn't available, so their failure kinda didn't matter.) Then Apple decided to just double everything in iOS, which made things tractable enough. OS X is mostly following the same approach, although there is a compromise mode where the screen is rendered at 2x resolution and then scaled down to fit the LCD.

[1] See http://dcurt.is/pixel-fitting