I know I'm going to get flamed for this, but is it me or have kids just gotten bigger?

I know that I've seen some 18 month olds that look like little 3 year olds. Should the age of the kid be the factor on whether or not it should be allowed to be a lap child or should its size?

If you as a parent are required to still use a car seat or booster seat until a child is a certain weight/height in a car, why shouldn't the same rules about weight and height and buying them their own seat apply to airlines.

lala