Naval protection and the decline of merchant anti-piracy armament

Why did merchant ships become less dependent on guns for protection against pirates?

Nearby naval protection, larger and faster merchant ships, and radio calls for help made attacks harder for sailing pirates to carry out.

Merchant ships became less dependent on their own guns where naval ships could be relied on to respond. The Royal Navy often supplied that protection. Increasing merchant-ship size and speed also made it harder for sailing pirates to catch their targets. Radio allowed a ship being followed to call for warships, while piracy persisted farther from effective protection.