Why are some lawyers driven to work such long grueling hours?

We ask the question: "Why are some lawyers driven to work such long grueling hours, particularly if they don't have to?

Aside from those situations in which a lawyer (a) must work a considerable number of hours to meet billable-hour requirements; and/or (b) is driven to earn substantial income to meet office and/or personal financial overhead obligations, why do some lawyers, who are not faced with such impositions, or who have already met their "marks," work as hard and as long as they do?

Some lawyers literally just don't go home (at what one might consider to be a reasonable hour) !

• Is it because they don't want to go home and face what is there? - - in other words, the "devil" at home is worse than the "devil" in the office?  or, put another way, their office is their "safe haven"?
• Or, is it that they don't have a home to go to?  - - which we doubt !
• Or, is it because they love their office and/or work to such an extent that there is no place else they would rather be? - - which we consider to be so sad !

What excuse do they make to themselves to remain in their office hour after hour, well beyond normal closing time?