Why do people accuse a girl for provoking a guy rather than accusing the guy for misbehaving?

Because, my dear, it's a common known fact that men are pigs and that there is nothing that we can do to change this - therefore, it's up to us women to either cover ourselves (which really wouldn't do much for their behavior, as you've just discovered) or slap them and then slap their mothers FOR not slapping them sooner.