[hnick]

I think that as the number of choices and opportunities in life go up, the opportunity cost of giving up a portion of this naturally increases. You might end up with "more" overall than past generations even after having kids, but loss aversion makes you feel the part you're giving up more keenly which steers some people away.

It's the same reason some people can't just relax and turn off. We're able to be so efficient/productive now, 30 minutes "wasted" costs a lot more now than it did in 1990 or earlier.