I come in on the weekends sometimes, because I'm bored or lonely or have work that needs to be done. I get paid for the privilege and I love my job, and it means I never have to stay past 5 during the week. Granted I work in academia where the norm is to stay till 8:00 and weekend work is necessitated by the projects we work on, but I personally don't have to. If I had a family things would be different though.