From the outside, having kids just doesn't make sense. Financially you'll be worse off, at the cost of sleep, more stress, no time for yourself, only as happy as unhappiest child, etc etc. The daily drugery of cooking, cleaning, homework, at the sacrifice of your own life? Just doesn't appeal.
And there's no guarantee your DC be happy or healthy. Or want to stay in touch when they grow up. Or give you the happy family moments you'd like. By thousands of posts on MN, you're likely to be unappreciated at best but at worst your DH will have an affair/leave/become abusive and you'll then be a single parent.
My friends lives, again from the outside, look worse now they have kids. They've aged really quickly. Lost a lot of themselves. Of course they love their kids, but that's because they've biologically evolved to. No one else will love their DC like they do. Everyone else's kids are annoying - but theirs are angels.
Several friends have said 'I wouldn't be without my Little Johnny, of course, but if I could have my time again....'