You can't have an apathetic population get involved (in society) when they have lots to lose but little to gain. Partners coming home at 11pm and leaving at 5am isn't a "partner". Why would any one want to raise a family and ensure the continuation of the society when you're in that situation.

Basically what they did and continue to do is forgo roughly half their potential workforce and half their overall potential because they could not bother to make things even semi-attractive for women to stay employed beyond 30.