[SkyMarshal]

I also wonder if it's related to decreased birth rates in modern times - parents have fewer children than a century or two ago, so losing a single child to an accident of some sort is much more costly to the family, hence the increased risk aversion.

[spin]

I have another explanation: If you have more kids, you don't have time to watch after them all as much.

[mark-r]

I doubt that losing a child has ever been less than awful no matter how many you have.

[SkyMarshal]

Certainly no less emotionally awful, but less economically consequential to the family. Incentives matter.