I'm sorry. I mean that Facebook could provide more lifestyle benefits and corporate culture in which an employee would not be compromising their career or need to career optimize around family planning opportunities. Maybe this is too utopian to expect.
It's not as though Facebook is coercing people to do this in order to lengthen their careers. People will do it anyway due to a culture that already exists and because they want to; from that perspective, Facebook is providing a nice benefit for people who don't want to compromise their career. It's not for you to say that this decision constitutes "abnormal" behavior - its characteristic of a lot of peoples' rational career optimization.
I'm not claiming it's altruistic, but I am claiming it's a poor heuristic for judging a company.