Indeed they help you most often during turbulence, I think that's more common than a crash. I was traveling recently with my 2 children, 1 and 2.5 yr old. When the child is over 2 he needs to stay on his own seat, but the seat belt does not shrink to the size of the child. I think it was at least 10cm loose and they refused to give us a baby seatbelt because of rules. Simply stupid, with all the safety measures that you have in a plane why is this being overlooked?