A child also can't obtain a credit card and pay to hook up an internet connection on their own.

If you want a true apples-to-apples comparison using your list - you've already purchased beer, cigarettes, liquor, a machine gun, adult books, and a motor vehicle and brought them all home. At that point, it is your responsibility as a parent to ensure your children do not use any of them. Why should internet access be any different?

What you're really asking for is an adult other than you to be present in your house to ensure your children don't use things that you don't want them to. That's called a nanny. Unfortunately, the way in which you want this to work is for every house hooked up to the internet to be required to have a nanny.

No thank you.