"So you're arguing that obesity, neck pain, loneliness, divorce, stress, and insomnia cause long commutes? Or that some factor causes both? What might that be?"

Poor decision making skills. Excepting possibly neck pain (and even then I could work it in), that could underlie them all, and there's a certain amount of evidence to suggest things like willpower and discipline exist as at least statistically-distinct entities, even if you can't quite point at the willpower organ.