The Duggars are trying to win a prize.
They have their older kids take care of the newborns, so mom & dad can "get started" on the next baby...
Not to mention "breastfeeding? What's that?".
And I agree with most of the preceding post, except for the implication that getting married in one's 30's is enabled by the consequence-free fornication that only birth control can provide.
The American economy has changed, our culture has changed, the maturity expected of a child at age ___ has changed, and so on. It's easy for youths to be employed when 95% of the economy is agriculture. But what about more advanced economies, with jobs that require skills? Either one needs a degree to be qualified for a job, or at least the education required to be able to work in a given profession.
Even if degrees were mostly bunk, I don't think most 16 year olds could write software professionally, or do any other professional job for that matter. You have to learn somehow, and it takes time. And children need to spend their school days on the basic well-rounded education, which only allows so much time for hobbies, side subjects, and side projects.
Kids under a certain age just need to play -- that's an absolutely ideal case for children. In other words, if you only have 1 child and you have 500 billion in the bank, and you want your child to be as successful as possible: then you really need to let him play. Creative, unstructured play is the best thing by far for children under a certain age.
Basics like farming and homemaking are "free" if the child is raised practicing these arts. But modern careers require more schooling -- on one's own and/or in a formal setting.
But even when the man's career is set, then young couples have to find each other. It's not easy. Traditional Catholics are so spread out. And even some Trads at your local chapel can be quite unsuitable -- they might have social, emotional, spiritual, physical, or psychological issues. And some might be Trad in name only. And even a young man and a young woman at a Trad chapel might be healthy in every way -- but just not be suited for each other. That happens too. You are comfortable with what you're used to, etc.
So finding a suitable spouse often takes time measured in years.
And as the saying goes, Irish birth control is "getting married late". (Ireland used to be a very Catholic country. Another related term: "Irish twins" which means a person has 2 children in the same calendar year.)