So much this. Chainshot was highly effective at taking down masts and sails, effectively immobilizing the target. If you fired a chainshot towards the mast, chances were really high that each ball would hit 9n each side of the mast, with the chain tearing off the mast itself. And even if you missed and hit only sail, the chain would rip out a huge chunk of sail and any rigging it hit as well.

Source: I used to play Cutthroats a lot back in the day.