Why wars cluster around canals, ports, and maritime communications

Why do so many conflicts center on canals, ships, and ports?

Because they control communications and enable heavy or bulky cargo to move with much less friction and infrastructure than overland transport.

Communications are the first part of the answer: canals and ports organize the routes on which military and economic movement depends. Water also provides a naturally low-friction surface for carrying heavy and bulky cargo. Equivalent overland movement demands durable roads, bridges, and much more built infrastructure. Conflicts therefore cluster around maritime chokepoints because control of them shapes military mobility and the economic flows that sustain war.