"What's even more striking is that despite a good deal of practice, they don't seem to be getting any better. They can just about cope by the end of the lesson but by the beginning of the following week it's gone. I've thought long and hard about my teaching technique, but they seem to be able to retain other taught skills perfectly well. So I'm a bit baffled."
Why think for yourself when you have the University of Google / Youtube to answer all of your questions without thinking critically about it?
As I've mentioned in a previous post people in general have access to practically all the information they can ever need thanks to smartphones and the internet, but the underlying simple principles are neglected - everyone can use a GPS but how many can map read?
K.I.S.S.