I feel like I am retarded.

I am uncapable of understanding why people under the age of 14 years should not have intercourse. I also don't understand why some people with autism or mental illness can't have relationships or intercourse (according to the law).
Can someone explain, please?

I know some people with Autism can't speak or express themselves, so if someone touches them, they are uncapable of saying they don't want to be touched.
So I kinda understand why people in general think autistic men and women should not be dating or having intercourse.