People worked that hard when families often had 3 or more kids. The difference is one parent could afford to not work. We've let corporations "optimize" that away.

Phones have had parental controls already built in forever. My sister is a busy executive who commutes daily and she didn't let her kid have a phone until age 13, and when they bought an Android phone they signed up for one of the (many) existing parental monitoring apps. Which for ex will notify the parent when their child gets messaged from a new person not in their existing curated contact list. So their phone is only used contacting their close friends at school. Parental monitoring and controlling usage on sites like Youtube and Facebook is a long solved problem, if the parent put any basic effort in.

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.