Regarding a full ditch and recovery. That was a challenge for me. I would perpetually throw my gear into my grandfather's apartment complex's pool and do it over and over again, until I got it quickly and easily (my Dad also required me to do this). And while this may not be a skill I will use everyday. When I accidentally got a piece of monofilament wrapped around my tank valve, and was able to easily whip off my rig, get the monofilament off, and don it again in under 30 seconds, I was glad I had practiced a zillion times in a pool.
I think the point of this is that the argument Thalassamania et al are making is that the mastery of these skills were once the norm. This norm was not established so that divers could do sat diving at hundreds of feet or go deco, they were the norm for all diving. A lot of these skills apply to situations that most of us hope to never be in. But, I personally would rather know what to do just in case (and be able to calmly do it), than be the the one in a million who gets myself into a bad situation and isn't comfortable getting out of it.
Effectively, training is about balancing risk. There is inherent risk in the sport, the question we as divers, and consumers of the product put out by PADI, NAUI, etc have to ask ourselves is what is the cost/benefit? I personally feel that the couple hundred hours of training (not to mention my Dad's tests) I have gone through was worth every (frequently frustrating and repetitive) moment and every penny, if it means that I survive, or am able to save another in a situation.