We depend on the world. Not at all. The original Kibbutz idea was Jewish, but NOT homogeneous. There is a great difference between Ethical Cultural Jews and Hassidic Jews than there is between Catholics and Unitarians. Also, many intentional communities had a wide range of people participating.
Families serve as the main tool for that function.
Only because the economy needs it to be that way and religion and the government serve the economy. This is wrong, at least in many states. Polyamorous communities are discriminated against, and in someplace outlawed. There have been cases where the children are taken away because the group-raising method makes them unfit. I wish I had the URL, someone with more energy than I could probably track it down.