Folks are saying "it's a multimillion dollar movie, they'd use a meter!" but from some of the anecdotes from the guys actually making the movie, I get the impression it was more improvised, more of an adventure to make as well as to watch. They'd take the second camera crew and rush off when on location at the last second to get some new idea shot, and so forth.
It had a lot more of a low budget feel, is what I mean. It's the kind of thing where many shots are on locations or outside, and not on a set. You look at the light you have and you can tell what you need (with practice). That, coupled with just having so many years of experience -- I can totally believe he didn't use a light meter. I hope to be that good some day.