I'm not saying all men approach simply because they want to have sex. I'm saying all men who approach with no other information do - because that's all they can possibly know about her.

If you're at school and you approach a woman, you already know you two have similar levels of ambition or possibly even a similar interest (if you have the same major). Same if you are both engaged in a hobby. But out in public? You know absolutely nothing about her. Which leads me to the conclusion that the only thing you can possibly know is that it's based 100% on her appearance and for men - being attracted to a woman also equals wanting to have sex with her.