A child might not be as old as an adult, but they have a body - they have brains! Adults are currently putting our children into conditions where they are being forced to become dimmer by certain vaccines, which they can't do anything about. I feel personally that this is wrong and that it should be the child who says - not the adult.
If the age of consent is lowered then a parents ability to act in their child's best interest is removed.
This could lead to a child refusing life saving treatment or treatment that may have avoided life long problems. All because they were not mature enough to understand the consequences.