Why can't your job be one of those? Why do your employers feel entitled to free labor?
There's also a nagging bit that says "the wife and kids are asleep, there's nothing stopping you from sending those emails/working on the fixes you were looking at earlier". Then one email becomes four, a feature is completed/tested/checked in, and it's midnight.
It's not that my employer feels entitled to free labor, it's that my brain can't stop thinking about work. My job has somehow become my hobby.
A friend in Sweden is sometimes on call overnight, but is expected to sleep. If he's called, he gets the rest of the day off, because of Sweden's implementation of the EU law these rules implement.