My very good friend and I were having a walk and she explained to me this concept called "The Ladder Theory".
Apparently, men have one ladder while women have two.
When a man meets a girl, the man puts her on the one ladder on a step the height of which is determined by how the man ranks her according to his criteria of whatnot (beauty, intelligence, humour...etc). Regardless of where the man puts the girl on the ladder, the man will want to shag her if and when the opportunity presents itself.
Women have two ladders, one for 'friends' that rank the men in their lives who they will never have sex with, and another for 'sex', as in men who they will want to shag and/or have a relationship with.
It is possible for men on the 'sex' ladder to be demoted to the 'friends' ladder while men trying to jump from the 'friends' ladder to the 'sex' ladder will always fall into an abyss from whence they will not be heard of again.
I am not going to jump between those two ladders.