It's good these questions are asked. It is in our society's best interest to expect child-rearing and marriage. When those start to disintegrate and disappear from public expectations, there goes your birth-rate. And up go the percentage of babies born out of wedlock.
If you can't have them or circumstances have led to other decisions, just smile and be thankful that you live in civilization that's not going to make itself extinct by failing to do something so basic as produce offspring.
It's also in society's best interest to expect healthy lifestyles and reasonable height-to-weight ratios, but if someone asks me why my butt is so big, I'm not going to just smile and be thankful that I live in a civilazation that cares about these things.
One never knows if someone has lost a child or has tried and tried but can't have them, etc. People should just mind their own business.
Oh, man. What a load of tripe.