While we say that we only care about results, in reality we tend to value results based on the effort we perceive people put into a task. Artists get asked “How long did this take you to paint?” and workers that accomplish little but leave late are seen to be exemplary workers. Some psychologists refer this to the “labor illusion”.
And the ubiquity of complaining about long days at the office suggests that people tend to apply this idea to themselves, too, giving more weight to time spent laboring than actual accomplishments. Because one, of course, does not necessarily lead to another: Consider the recent study, for example, that found office workers routinely fib about working 80-hour weeks in order to get ahead at work. Their bosses mostly fell for it, suggesting that they couldn’t tell the difference in terms of what their subordinates actually got done. (post)