Why piracy did not surge during the world wars

Did piracy flare up during the First or Second World War away from the main fleet concentrations?

Not significantly, because most maritime regions remained under the control or patrol of one dominant fleet or another.

Wartime concentration did not simply empty the rest of the oceans. Areas outside one major fleet's immediate control were generally watched by another state with its own security interests. Japanese attention to piracy around China provides an example of regional enforcement continuing during wider conflict. Sea control was a distributed political condition extending beyond the position of the largest battle fleets.