Me too! Just because a 4 yo CAN reach the lever of the ice cream or the spoon on the buffet doesn't mean that they SHOULD be allowed to touch them and serve themselves -- especially considering what else they are doing with that hand while waiting in line to get to it.
One of the reasons we generally don't do buffets. I've seen way too many under-supervised children with hands in places they don't belong. At least when my food comes from the kitchen I'm relatively sure that it hasn't been mis-handled.