actually have, for a few reasons. Once you have a child, you grow to love them and can’t imagine life without them, and sure as heck aren’t going to say that life would have been better without Child A or Child B. Also, it’s human nature to be reluctant to admit you were wrong about big decisions — people tend to look for ways to justify those types of decisions to themselves, as well as to others.
Finally, some who are LDS, like most on this board, may feel it is wrong to ever state that they should have had fewer children, even anonymously, given the Church’s culture and history of encouraging big families with lots of kids.