Paul Beakley there were lots of merchants who could arm themselves, and there were no laws against doing so, nor would anyone look askance at it. The operative decision point was profit. Guns meant weight not dedicated to cargo and the crew to man them were extra sailors who needed paid, so when the sea lanes were safe, not much need. During periods of war when the enemy would commission privateers, or immediately after a war when large numbers of naval sailors were discharged and out of work, and would turn to piracy as the only job they knew, the possibility of discouraging a pirate could be worth the expense.

The vast number of pirates were tiny operations. Coastal boats, primarily rowed (looking an awful lot like Somali pirates today) that would dart and grab. No merchant would fight off Queen Anne’s Revenge, but that’s why those pirates were legend. Most were just punks with boats, and a coupe guns could send them off.

The East Indiamen were the best armed (the size of a fourth rate SoL with armament roughly equivalent of a small frigate) because they had the longest voyages with the most valuable cargo, and being large ships operating in the tropics already had excess crew.