Beatcal - no one reports broken arms and concussions for car accidents either. How many children sustain the same injuries in sports activities or just from playing?
It's pointless to discuss this. I think under two year old children should be in car seats on planes, but they aren't required to be. Statistically, they are safer on a plane than traveling in a car, no matter what some FA told you or what you believe.
Go over to the family forum on a Cruisecritic.com. You'd probably enjoy some of the ludicrous discussions about bringing a car seat while cruising. The majority of posters there seem to feel it's unnecessary to restrain a child while taking a cab in port. They'll just ask the driver to be careful and go slowly, and they remain convinced they could hold onto their child if there was an accident.
Apparently, the laws of physics are suspended while one is on vacation.