One aspect is that couples should not feel like they have to justify their decision to not have children. My wife and I decided from the beginning we wanted children but we were going to wait a few years to enjoy ourselves as a couple first. Being that it was my 2nd go around at this whole marriage thing i was 33 before we had our daughter. In Hispanic circles, particularly Cuban, that's older than dirt to start having kids.
As it turned out, our daughter was born with autism and that quickly put the brakes on any notion of having more kids. Not because we were afraid of having another one with special needs (the likelihood is very high), but because we knew she would need more time and attention than "normal" kids and that wouldn't be fair to another child. In retrospect, it would've been sensible to have another child because nothing keeps me up at night more than knowing that when (not if) something happens to us, there's no one to take care of her. My only sibling passed many years ago and his spawn are as worthless as t*ts on a bull and my wife's an only child.
As you can see, there are indeed many factors to consider when deciding on whether to start a family or not. I just wish people would stick their opinions where the sun don't shine.