Slon, you're picking nits, yet not really addressing the issue. The fact is that the State has to determine a guideline by which most individuals can be determined to be able to make good decisions for themselves. No, there is no "magical" change that occurs on the 18th birthday. However, most individuals who hit 18 are able to make good decisions for themselves. 16? Not as many. 21? Probably more, but the difference isn't that significant compared to 18.

As far as 10 year olds being able to make decisions about sexuality; that's clear if you actually examine child development.

__________________
When they come a wull staun ma groon
Staun ma groon al nae be afraid
Thoughts awe hame tak awa ma fear
Sweat an bluid hide ma veil awe tears