Why interwar submarine danger did not guarantee escort funding

Why did the Royal Navy not treat submarines as decisive in interwar force calculations?

The perceived enemies and shipping geography weakened the immediate case, Germany initially had few submarines, and Treasury pressure forced competition between treaty-limited destroyers and unlimited but slower sloops.

Britain repeatedly sought restrictions on submarines, while the apparent interwar threats from Italy and Japan did not map neatly onto the Atlantic routes most vulnerable to commerce warfare. Politicians could point to British attempts to outlaw submarines and ask why additional anti-submarine ships were still necessary. Treasury choices also framed sloops and destroyers as alternatives even though the Navy wanted both. Small sloop programs consequently served as practical laboratories for anti-submarine warfare and minesweeping before Flower- and Hunt-class construction accelerated near war.