Age difference?

Liz
I keep seeing posts that it's okay for a 16 year old and 20+ year olds to date. Firstly, it's illegal in some states. Secondly, 16 year olds (or younger 🙄) have not developed fully. I feel like it's bizarre that an older man or woman would be attracted to a younger adolescant. I understand there are some execptions, but men who tend to date teenagers and say "age doesn't matter" creep me out. I'm open to being enlightened. :-) 
(Also I do believe age gaps in adults do not really matter as both people are fully developed physically and emotionally)