I've found on non-US airlines, the baby extension is the norm. To me, that seems like the safest way to go. Like you, I'm amazed how everyone else on the plane has to be strapped in, but US airlines say it's cool just to hold a baby in your arms during takeoff and landing.

Unfortunately, the sad reality is that if someone were to go wrong, it probably wouldn't matter either way. But hey ... air travel is the safest way to go!