Never heard about wire-controlled torpedoes before, but indeed this makes total sense. Radio waves don't travel far in water. There are quite some spectacular systems built to contact submarines underwater [1] operating in 3-300Hz radio frequencies but antennas are kilometers long consuming megawatts. Wired-controlled torpedoes would be able to easily get target guidance from the submarine. Since torpedoes don't move fast (unlike missiles) un-spooling and long distance wires should not be a problem (wires can have neutral buoyancy).

1. https://en.wikipedia.org/wiki/Communication_with_submarines