Be that as it may, the age in the US where you are considered an adult is 18. Many states do have a lower age of consent, though those are often conditional (ie the lower age of consent doesn't apply if the partner / potential partner is over 18). I remember Dr. Drew on LoveLine saying that the average* age of biological adulthood for young women is around 16, and that he considered 15 and younger to still mentally, emotionally, and physically to be a child. I think we can agree that, in this day and age, in the USA, no one over 16 should be having any kind of romantic contact with a 13 year old.The kind of people who have the drive to take the power they desire are often also the kind of people to decide that certain rules don't apply to them. This is seen in a variety of situations.
Also, the age of consent is very much a an artificial cultural construct, and not a biological fact. In Austria, Germany, Portugal and Italy, the age of consent is 14. In Korea, it's 13. In the Phillipines, it is apparently 12.
* - I don't know if his average was mean, median, or mode, or how biological maturity was determined, though I think it had something to do with stabilized hormone levels and scans of the brain; perhaps by age 16 it had developed enough to be considered 'adult'.