Why? If Canada and the Military are using them.....
Firstly, they are not 'using' them, they are 'wearing' them, which is an entirely different thing. Secondly, the training is superior and not classroom based.
The idea that somebody who is
not a sports diver, will take a mouthpiece and purge it and then start breathing underwater for the first time, ever, in a real emergency, seems very far fetched. I say that as someone that has never used SCUBA gear and has done HEED/STASS training.