Also, and Carmack nails it, people are different. You might think it's unhealthy, or unnatural, but some people are obsessive, perfectionist, focused or just really passionate about something. Also, some people are just better organized. Again, Carmack's right, you probably can't be at your peak for extended periods of time, but there's plenty of things you can get done that don't require your peak.
When this issue is raised from concern of people being taken advantage of, fine, I agree. But just because some people can't do it, doesn't mean no one can (just look at the extreme range of physical and creative abilities that people have). And, like all other life style choices, what's the point of judging other people?
Keep in mind that I'm the sort of person you are indicating already. I sleep little and don't care much about work/life balance. When I've worked on teams that are burning the candle at both ends, I am able to hold out longer than others and usually end up carrying things over the finish line.
That's the point of my comment: Even for those who ought to thrive, things start to break down, and no amount of energy or toughness changes that. We are human. I want to warn/remind other engineers that these practices are unsustainable. Hell, I want to remind myself of that after repeating this work to the bone/burnout cycle so many times.