OR you got dudes who are simply handsome and anti-social. They can have good convos...but they're too shy or simply dislike talking. A lot of women gravitate to mysterious, mercurial guys but if you're 100% aloof they'll quickly walk away lol
This used to be me

Was always fat and had low self esteem but had no problens interacting with chicks because I figured their was no attraction so therefore no pressure for me.
Started losing weight and chatting up chicks at parks and then would realize when it was too late that shorty was giving me an opening to get the digits

That is another way guys get frustrated..
You have to have good body language skills...most women will try to make it obvious as they can but not too aggressive so you kinda have to read her well.
Not every woman makes direct eye contact with a dude she likes...some will linger around in hopes you see her.