Why are 18 year olds considered "off limits" to older men?

If they respond to an older man's game or the idea of marrying young appeals to her, why would it be grooming if she is 18? Remember, she wants it. No coercion, sugar daddy, rape, anything like that.

18 year olds get taken advantage off by insurance salesmen, taking out loans, being recruited by military, vote, etc. They should be old enough already at 18 to make decisions like these or the age of becoming a legal adult would be higher.

So, why the accusations of older RP men grooming or taking advantage of these 18 year olds? Should they only go for them after college? Or is it based on individual maturity?

Edit: Something I noticed in this thread is BPers generalizing about 18 year olds being too immature to handle being with an older man in a relationship or generalizing about the older man taking advantage and manipulating the immature 18 year old.

Sounds an awful lot like A18ALT and AOMALT.