Oh for pity's sake
Yes, some safety laws are ridiculous, but some aren't. They've been trying to make this law for 8 years old since the first car seat law was introduced. But parent's whined and cried and worried about how their little darlings were used to being "big" kids and wouldn't want to go back to the car seat.
The fact is, without the law, many people wouldn't bother, because they wouldn't realize it's not safe. And even still, parents want to take short cuts for their own convenience. And then they use the excuse, "when we were young, we never had car seats and we survived" But what about those who didn't because the technology didn't exist?
My great-great grandparents had 9 children and back in the day, no one thought anything of leaving a 2-yo child sitting up on a fence, until one of them went splat...but the other 8 survived, so there couldn't really be anything wrong with it.