As noted later, it's difficult to draw a correlation between lap infants and fatalities as, a) incidents with selective fatalities are rare, and b) there are other factors that more significantly impact survival in an incident.

Regardless, there have been injuries and fatalities with lap infants that could have been prevented if a child was secured in a seat. I understand the argument that its relatively safe to hold a small child and that's how my kids preferred to fly when they were <6 months old. On the other hand, if you're going to let a kid sit on a parents lap, why bother with seat belts for other passengers? The risk of injury is much, much better than in a car.