Why work where you aren’t happy?

There have been several discussions lately started by people unhappy with non-technical aspects of their work environment.

“The boss is sleeping around.”
“The secretary preaches.”
“The CIO ignores my advice.”
“There’s no Pepsi in the drink machines.”

Okay, that last one is a legitimate issue. But I wonder why so many people stay in jobs that apparently have them on an all-Maalox diet. If you’re one of these downtrodden souls, or if you’ve been in this situation, what are the reasons why you don’t look for another job?