New parents are like apprentices that got matched without a master. If they're lucky, they band together, tackle the unknown, and build their credentials together. It's pretty amazing to witness-- newbies shoring each other up, learning from one another and building on each others' confidence. But damn if it isn't inefficient.
By the time you've got some parenting notches in your belt, first time parents scream rookie-- they bathe the baby, run errands, and entertain the baby together. They can't fathom life with a baby and a toddler because every task takes both of them at this point.
Parents that have banked some experience can and do tackle kid care separately. Both to make time for individual interests-- you do the morning shift while i get to sleep late, i'll do the late one so you can read; and because each can handle the mundane alone. Some things are certainly easier with two and some are more fun, but by now the more experienced parents know they can tackle most childcare on their own.
This is more efficient and often makes the kids lives happier-- someone runs around town to buy groceries and hit the dry cleaner while someone else stays back to let the kids play around the house or head to the park. In it's efficiency and productivity, it loses a little bit of the connection that new parents can be blessed with. Because not only are they engaging in tasks side by side, they're learning a craft together. It's like going to a pottery painting studio-- but with soul.
In the spirit of thinking i know it all as a parent, i've offered to take my friends' two daughters to the zoo with us this weekend.