You're right... but start-up culture glorifies the long hours and epic all-nighters[1], that to do otherwise would have you tarred a slacker[2].

[1] "One of the most pervasive myths of startup life is that it has to be all consuming. That unless you can give your business all your thoughts and hours, you don’t deserve success. You are unworthy of the startup call. This myth neatly identifies those fit for mission: Young, without obligations, and few if any extra-curricular interests. The perfect cannon fodder for 10:1 VC long shots." http://37signals.com/svn/posts/3106-all-or-something

[2] "Startups Are Hard. So Work More, Cry Less, And Quit All The Whining" http://uncrunched.com/2011/11/27/startups-are-hard-so-work-m...