Some people enjoy working like that, and enjoy their jobs enough that they don't care that they're actually working.
The extreme example is John Carmack, who according to the book "The Masters of Doom", would crank music all night, and drink diet pepsi (early days of id, grant you, I don't know how he works now) while programming. He rolled in the office at 4pm and stayed until early morning.
There's nothing wrong with working crazy late hours if you enjoy it.
The problem is when you start at 8am, work all day, waste time in meetings - then have to stay til 10pm every night to meet some deadline so that a sales guy gets a bonus.
There are lots of things that "makes life more fun". I find that not having to work nights and weekends, but loving so much what you do and the problems you work on and the people you work with; makes life even more fun.
