People who work too hard

Lately I've run into way too many people who work 12 hour days. Why? Because their bosses tell them to? This makes me feel really lucky as I only work 8 hour days. The question I always wonder is why do they put up with this? I worked longer when I felt my business was struggling or I felt I wasn't very productive. Now I try to work smarter not harder. I also have a significant other which helps me put my foot down a little harder on these kinds of things.