So what ship owners are going to put their ships up for, cross Atlantic convoy duty or cross Pacific, when they won’t even risk the gulf of Aden against Third World Terrorists?
Simple - the government compensates shipowners for losses.
This happened to my great grandfather. He, a Spaniard, owned a few interisland vessels in the Philippines (500 tons or less). USAFFE chartered all of them in 1941. They offered compensation for loss or damage. As it happens all of them were sunk or destroyed by April 1942. One was burned at a pier after a Jap airstrike, one was driven aground by a patrol boat, another was boarded and seized, and the Japs lost it later.
In 1946-48 he was offered cash compensation or new surplus hulls (ex-minesweepers). He took the ships.
That was the deal in WW2.