Because we see boobs daily, no matter where we look. Your mother? Boobs, The girl up the street, girl at the Mc Donalds Counter, Woman in the office, it's impossible not to notice and more impossible to remove boobs to tell a gender between male and female.
Folks in my country don't wear Speedos with the exception of folks who do visit to wear them as their whole custom.
Lastly, just mod them in man if you are going on a Tyrade.