Should people under 21 need a parents consent for tattoos or cosmetic surgery?

In most places people over 18 do not need parents' consent.

The question is, when are people old enough to make responsible decisions about their bodies? Perhaps it is earlier than 21 or 18. If a parent is legally responsible for their children until they are the age of 18, then it is in a parent's best interest to be on top of what their child is doing to their bodies.