Here's a tiny bit of explanation second hand from USN about why the USN does not use them - too much chance for things to go wrong, although that's not surprisng they would say that considering that's what the Soviets said happened on the sunken submarine being discussed.
https://www.nytimes.com/1989/05/04/world/rescue-capsule-save...
On the flip side between where you can get out in a survival suit, where rescue submarines can get to, and places where the people tank will go crunch before you hit the bottom, pretty much everything is covered for USN submarines; it's a very safety conscious community.
