I did to some extent share with one close friend who lived in the same village, but all other friends were a drive away and it only really works if you're close by. Getting out of the house with everything you need to be at someone else's house is too much in the early days.
Also, some had family help so didn't need to do this, so wouldn't.
The divide is, I would agree, those who have family living nearby.
We've moved around so much, mainly for DH's job, that I'm not geographically close to any of my really good friends. It doesn't really work if you have to drive 2 hours to get there. We don't have family back up and it's been brutal.
I think the fact that many people move away from family for work is the big killer - leaving many first time mums totally cut off when they have a child. Right before I had kids, my only friends came from work, which was a 1 hour drive away from where we lived (DH worked in the opposite direction so we lived in the middle). That was no problem to socialising (there was a train) when I had no kids but was a huge distance with a baby.