Piracy is profitable without some sort of overwhelmingly present and powerful force to dissuade it. Somalians wouldn't do it if it didn't work sometimes, and they've got everyone on their ass - if the US, now, can't functionally stop their piracy, what stops people from piracy in AnCapistan, when there's no monolithic centralized army?
Um, being allowed to carry guns/weapons, for one. The main reason piracy is such a problem around Somalia is because cargo ships aren't allowed to carry ANY weapons on board if they wish to be able to dock at international ports (government law/regulation). It's why all they can resort to to fight armed pirates is water cannons, noise makers, and just locking themselves inside strongholds on the ship. It's also why Somali pirate ships stay WAY the f*ck away from any military ships.