Sure, many people don't conceive the 1st time, but of course it could happen the 2nd time, and sometimes it may take 100s or 1000s of times. But many families might be glad to have many children with ages close together, or some may okay with having "baby after baby after baby." Don't forget human fertility is fragile and can fade quickly with age. Or something may go wrong, such that she can't have any more babies, so it was good to have so many while they could.
One some large family comebacks webpage, I read one about "Haven't you had that baby yet? Answer: Yeah, and this is the next one. See if that doesn't make their jaw drop."
I don't believe in use of birth control and am open to the prospect of having a big family, so if a baby conceives the very 1st time of sex after birth, so much the better. More and more people would be glad to live, so why not respect the body's natural reproductive rhythms and to welcome babies to come when they come, like worked so well for our ancestors? I don't believe in hindering the natural human fertility around the world and believe in embracing and celebrating humanity's soaring natural increase.
Anyway, not everybody conceives right away. Doesn't it often typically take a year or 2 or more? Breastfeeding supposedly helps naturally space babies somewhat, and surely God meant for most babies to be breastfed until they can move on to solid food. So I accept breastfeeding in public, as is common in developing countries, still more pronatalist than we seem to be these days.
Perhaps the pill messes up more people than you think? Not exactly the most popular topic of conversation is it, to admit to being conned or duped, whether by a financial scam, or by misleading contraceptive propaganda? Some women may have destroyed their fertility, but since they aren't trying to conceive anyway right then, fail to notice, and then they can't get pregnant later. Is it then old age or what?
A guy I once worked with, said his wife wanted 6 children. Of course I told him to go for it, he wouldn't be sorry. A guy at a recent Walk For Life said they have 4 children and don't use birth control. Could be 6 or more by now? A friend told me that they decided to try for a 5th child. And a couple at my present Church is expecting their 5th child, a girl, in a few weeks. I've been to Churches with families of 6, 8, even 9 children.
But if people have any hopes of possibly having a large family, they should allow conceptions to occur as much as possible, because the human fertility is not so certain as to just pop out babies on demand, nor are many people near as fertile as they think they are. All reasons to consider that "birth control" probably isn't worth the bother anyway. Most all parents love ALL their children, no matter how many they might end up to be. Whatever happened to "faith babies" anyway, a term that has a somewhat different, but related, meaning in the sci-fi movie GATTAGA.