Although assisted to a degree by overall experience in the air, I've always considered EOLs a skill that is predominately honed "on the job".
In an ideal world, schools would be staffed by high time instructors - and by that I mean having a high number of hours instructing.
EOLs and numerous other procedures that would undoubtedly make a more rounded pilot would be practiced until perfect.
But the reality is that there are not enough experienced instructors to meet the current training demands on their own, and people are paying for their own training so perfection is met by compromise.
The major difference between demonstration and teaching an EOL is the degree of repetition required. That increases significantly:
1. the statistical risk of something going wrong
2. the long term fatigue and damage that even successful EOLs place on an airframe
3. the cost to the student by several hundreds of pounds through paying for the extra flight time.
The extra servicing, the non-scheduled maintenance, the insurance excesses, all must be met by a private operator. A cost that is then past onto the student in the hourly rate.
I'm not suggesting for one minute that cost comes before safety. However, once an acceptable level of safety is reached, anything beyond that is subject to question particularly if there is another option that is considered as effective.
Although I am sure there are such examples, there does not appear to be a spate of people injuring themselves and damaging machines in engine failures through lack of adequate training. However there are numerous incidents, of which this is one example, where both people were hurt and a helicopter damaged practicing for an event that does not seem to be occuring that often. And when tested, even those students that have not been repeatedly taught EOLs are still managing to successfully complete the procedure.
One presumes its a delicate moment explaining to the owner and injured parties that you wrecked their machine / brought about their injuries whilst training them not to wreck a machine and injure themselves in the very unlikely event that a similar incident occurred in reality.
EOLs are an essential part of any pilot's training. The question is how you go about that training in the most effective and beneficial way.
With regard to comments about professional pilots and their competence in EOLs: well that is an entirely different story IMO.