There is a big difference between "doesn't dare to" and "it's not practical/useful for warfare". There have been plenty of submersibles that went much deeper.

There is a big difference between "doesn't dare to" and "it's not practical/useful for warfare". There have been plenty of submersibles that went much deeper. People went down 10km in the 1960s. There is no excuse for the incompetence and stupidity of this titanic crew.