I think the reason may be generational. The current parents are majority Millenials, the generation which didn't have to shoulder a lot of personal responsibility like previous generations. Thus when it comes to their children they as usually place the responsibility on anybody but themselves.

Both parents working actually i think is a net-good thing - it teaches children to be responsible from early age. As my parents were both working - USSR - even when i was 5 years old i was already watching my 1 year old sister. And we were pretty typical at that.