Why supercavitation is difficult for submarines

Is there a practical speed ceiling for submarines because of water pressure and drag?

Supercavitation can reduce drag by surrounding a body with gas, but scaling the technique from a torpedo to an operational submarine is far more difficult.

Water resistance is the central barrier to much higher underwater speed. Supercavitation attempts to surround the moving body with gas or bubbles so that less of its surface contacts water. Very fast supercavitating torpedoes demonstrate that the principle can work at weapon scale. Producing and controlling a cavity around a full submarine, however, is an order of magnitude beyond the existing application.