You know?

Why is it that guys flirt with a girl and when the girl tries to let them know right at the beginning that she is not available and she just wants to be friends, take it as a personal insult and try to act as if they were not interested in the first place and it's the girl's fault for assuming so? We know when they are flirting.. They know that we know.. And we know that they know, we know.. So, why is this so confusing for the guys? I mean, tough luck buddy.. Some lucky guy got there before you did.. So, be a man, suck it up and don't act like it's my fault..