Originally Posted by
theddo
According to the FAA it's not a big enough safety thing, which makes it a comfort thing all-round.
Did you know that the safest place for your child on an airplane is in a government-approved child safety restraint system (CRS) or device, not on your lap? Your arms aren't capable of holding your child securely, especially during unexpected turbulence.
http://www.faa.gov/passengers/fly_children/
A lot of things aren't a "big enough safety thing" but are still very dangerous like guns, drugs, alcohol, smoking, etc. Some people choose to be extra cautious and pay to avoid these dangerous things.