I agree completely. And I imagine, before the internet, having an extended family would have a lot of "tribal knowledge" about all the little idiosyncrasies of raising children as well.
That can be both good and bad, though; I was talking to my stepbrother - who is 30 years my senior - and when he was raising his kids, who are my age, putting them on their stomach to sleep was the medically advised strategy. Today, that's considered a risk for SIDS.
I'd say that 90% of the benefit of the extended family would be people who would come and be a warm body to sit with the kid, or bring you food, at least for the first year.
