vodkaholic, are you serious? Have you never ever, not even in training, inflated a life jacket for real? So you really don't know how serious a tug is required? And you wouldn't know how to help a passenger who can't seem to inflate his life jacket on his own in a real emergency? This sounds unbelievable. Particularly since the cost of a regular (non-demo) airline lifejacket is somewhere in the order of 10-20 EUR. Yes, they're use-once so after that you need to throw them away but I'd say that it would still be worth it in training. Particularly if you combine it with a pool session so you know how it feels and works in the water.
yes i am being serious. we have had ditching training however, but we had to blow up the life jackets ourselves. i'm not sure if you have ever even work a life jacket like the ones that are on board an aircraft. they can not only be used once. they can only be 'pulled' once, sure. but they are resusable many times by manually inflating them.
also, with regards to what you say about not being able to move much or jump into water with the life jacket inflated. this is crap! i have done it! and as have all cabin crew. part of the ditching training is to jump into the pool with a fully inflated life jacket on. you can clap your hands together when it is inflated, you can breathe, you can talk, you can swim! sure, it's a bit uncomfortable but it aids your survival.