I'll offer the short and long version.
Short Version: Mind your own business. Parents should be able to parent how they want to. What another parent does in regards to car seats has no negative impact on you, in fact the reverse might be true.
Long Version: First off let me say, helicopter parents, if you want to strap your tween into a car seat/booster seat no one is going to stop you. But you have no right to force your helicoptering values on the rest of the world. Even most free rangers would put their young children in a car seat/booster seat anyway.
What you forget to is that every law has negative consequenes. For example, mandatory car seat laws have caused some to buy larger vehicles. These larger vehicles when they crash with each other are 3x more likely to cause a fatl accident. Not to mention there are better uses of the time of the police. This would also include patrolling cross walks and intersections near schools for those who choose to blow through them as kids are making their way to school.
Also many of those who seem very pro-extreme car seat laws are also very anti-vacination. How would you like to have vacinations forced on you and your kids? This is even a case where there is a much stronger argument for it as, the individual choice not to vacinate does have negative consequences on society. Not that I feel they are worthy of forcing vacinations.
Not to mention wanting to enforce that they are used perfectly. Many kids are more than capable of moving straps. I don't know about you but I prefer peoples eyes to be on the road and not the car seat. Another negative impact.
Nor should classes be mandatory. Classes are great for those who choose to take them who live in areas where they do lots of driving such as the suburbs. What you forget is that not everybody lives in the suburbs. Even some people who do might still not drive.
Nor should a hospital be able to have any say in how you take your child home. It's your kid. What if you live across the street and just want to walk across the street with them. What if the pick-up area is further away then where you live?
You also don't know what might cause someone to not use a car seat once or twice. What if another kid or pet is sick and they need to get to the doctor as quickly as possible? What if the car seat broke and they are on the way to the store to get another one?
Update: It's also occurred to me too that car seats along with larger vehicles give the illusion of safety. Thus there is further danger in illusions of safety because people then tend to take less other precautions such, in particular in regards to safe verses unsafe driving practices.