Why escort fleets so often need wartime crash programs

Why did the US Navy need escort crash programs in both world wars?

The number of escorts needed in wartime was too large and too costly to maintain in peacetime, making rapid small-ship construction unavoidable.

Peacetime governments struggle to fund the enormous escort force required by a global war. Reserve destroyers help, yet hundreds of corvettes, frigates, trawlers, and other vessels are still needed across multiple oceans and routes. Flower and Castle construction times show why simple small ships become central to emergency expansion while larger ships take much longer to deliver. Atlantic, coastal, Caribbean, African, Indian Ocean, and Arctic convoy commitments all had to operate simultaneously while escorts suffered attrition.