Why did Gibbs become a pirate in the movie Pirates of the Carribean?

Answer 1

Because he had become a miserable loser after he had his ship sail through a hurricane and everyone but him died. That's why he was stripped of his rank and became a drunk who has to make a living anyway he can.

Answer 2

I think it's cuz he had nothing better to do. that and pirates approve of rum....

(note: person~ you're thinking of Norrington not Gibbs)