Let's also not ignore that plenty of people are working 100+ hour weeks. Many Nurses/Doctors, laborers & construction workers, deployed military members, movie producers, financial brokers.
I've seen all of these first hand - hell I've done it for extended periods. Near Christmas of 2010, about a month after I got back to the Pacific from 8 months in Iraq (Those were 90-100 hour work weeks at a minimum), the Koreas got into a little fracas [1] and it looked like war time for PACOM. That first week I worked 136 hair on fire hours with 38 of those being straight through.
That's 20 hours working, 4 hours of sleep (usually on a cot in a meeting room) with meals eaten while reading message traffic and reviewing documents in the bathroom. The following months were better, but not by much.
In my experience 100+ hour weeks are usually less than 12 months and then a break. Often though, the break is short (a week or so) and it's time to start again.
So it's actually not that crazy, but you have to be committed. Most people aren't that committed, and I find that sad, as there is so much worth committing yourself to.