Do you realise how hard it takes to maintain eyes contact with a stranger of the different gender? It’s a method to test if she’s interested in you; somehow might seem rude to some people. You give her a good glance and when she notices you, smile at her. I can never do that.
How many guys can achieve that and out of them, how many are flirts? It takes so much courage to take the risk of being called a pervert or even being rejected nastily. After all, it’s the first step to make friends with your eye-candies.
The confidence it takes to succeed has to overcome one’s own pride; it will eventually boost the girl’s ego and you don’t know if she’s a bitch. But if you don’t try, how would you know?