Why treaties discouraged fleets of small carriers

Why did navies not build more sub-10,000-ton carriers for non-fleet duties?

Treaty rules counted them toward carrier tonnage because Britain and the United States feared that an exemption would let Japan build many small carriers in peacetime.

Several navies could have found useful peacetime roles for small cruiser-carriers or slower escort types, and even Australia or Canada might have considered them. The obstacle was strategic rather than a lack of missions: excluding sub-10,000-ton ships from carrier limits might have allowed Japan to accumulate a large force before war. Britain and the United States accepted limits on their own options because their greater wartime industrial capacity could build small carriers after treaty rules ceased to matter. Treaty accounting therefore traded immediate Allied flexibility for a tighter ceiling on Japanese peacetime expansion.