@dznz
Many grandparents work as well. Many grandparents don't live with their children. Older grandparents/great grandparents often don't have the energy required to manage a toddler for long periods.

Personally, I hate oversimplifications like this. It smells of Rousseau and is the sort of nonsense that gets passed around by educated but childless people.

This thinking logically leads to an "ideal" system where both parents don't have jobs and stay at home and raise their kids full time.