Because the expectations jobs have come in large part form the cultural expectations prevalent within the field. And your job's expectations can make you either unhappy or unemployed.
It also appears to make the assumption that the only reason someone would be so involved in their work is that they are sacrificing their personal life to get a promotion or make more money.
>We recognize that your willingness to allow your employment to penetrate deeply into your personal life means that you will inevitably become our supervisor.
This makes it sound like "non-501 developers" just lie back and think of England so they can get a bigger paycheck. Maybe some people just enjoy working longer hours.