Trust me, I know plenty of people who prefer to bring their elbows back. It certainly helps create a bigger shelf for the bar to sit on. Rippetoe is a big advocate of that style as well.
However, I prefer to Squat with my elbows forward, and have had much more success with this style. When I pull my elbows under the bar, it forces my chest up and really locks in my upper back in place. It used to bother my shoulders with a low bar position, but I've since addressed that issue. I'm only speaking from personal experience here.