Why the Type IV Hunt destroyers stopped at two

Why were only two Type IV Hunt-class destroyers built?

Because larger destroyers and smaller escorts were entering service in enough numbers to make the intermediate design unnecessary.

An intermediate escort class is valuable when either the cheaper or more capable type is scarce. The Type IV Hunt sat between corvettes and frigates on one side and full war-emergency destroyers on the other. Once both ends of that force structure were arriving in quantity, the middle design became insurance rather than a priority. The same logic applied to fourth rates in the age of sail, which were useful but hard to justify in numbers when enough third and fifth rates covered their roles.