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.
I'm not cabin crew but I've also never experienced how hard to pull. People have just told me "jerk" not "pull" or "tug". But I did do a maritime survival course and let me tell you one thing. If you ever need to ditch, do not inflate your lifejacket unless absolutely necessary. That means that you don't inflate it IN the aircraft, obviously, but you also DO NOT inflate it once you get outside. As soon as you inflate your life jacket, you effectively become completely immobile. You can't swim with the bloody thing on. You can't move about in a boat or raft. You can't bring both hands together in front of your chest to, eg., tie a knot. You can't even swivel your head around because without a crotch strap the jacket will ride up your chest until it hits your chin and cheeks (regardless of how tight you did the double bow knot). You're completely useless and helpless unless you deflate your life jacket. (Do you know how that's done? I have no idea. That's something you guys conveniently do not demonstrate... I guess the overpressure valve, probably located on your shoulder, will have a button or cord that you can push or pull to let air out.)
The only time you inflate your life jacket is when you're actually in the water, you need the buoyancy, there's no raft or anything else that floats close by, and your assistance is not otherwise required anymore. But if you feel that there's anything left that you might need to do, whether it is climbing into a raft or assisting somebody else, the jacket is going to be seriously in the way. And you can only inflate them once.