This was a major factor in my wife and I's decision not to have a child, second only to the stress it would put on our lives to have one, which we would rather do without (I'm not convinced I'm emotionally strong enough to deal with a child)
I do know a lot of people who are not having children for similar reasons
EDIT: There's also a lack of the idea that it's worth having children, i.e. many people don't believe there is any intrinsic value in having a child like they used to