the problem, Nipper, is that many people returning to cycling, i.e. they last rode a bike when they were kids, have vague recollections of the Cycling Proficiency course in primary school and have fallen for the generally held viewpoint that cycling is, per se, dangerous.
Because of that, they ride in a manner which seems to them to be "common sense", e.g. close to the kerb, moving in and out when encountering parked cars and "keeping out of the way" of cars. This may be exacerbated by their sharing of the commonly held views of drivers that cyclists "don't belong on the road", etc.
Much of what is in Cyclecraft is, therefore, counter-intuitive to them. I've helped adults (as well as children) to learn to cope in traffic and quite often, I've had to persuade them that the above way of riding actually puts them at more risk than the Cyclecraft style.
I started the Kids Club partly because I discovered that many of today's parents didn't have a clue about how to mend a puncture, tell that the headset was loose, how to use modern gears, replace brake pads and even how to use QR levers.
You have been lucky, but I suspect that you may not realise how much information and skill you have internalised, which other people without your helpful family background, may not have the faintest idea about.
The advantage of this book is that it answers pretty much any query that newcomers/returners might have and gives very thorough and justified explanations of how riders should behave in various conditions. I still dip into it regularly, even tho' I've been on two wheels, either pedal or motor powered for far more years than I wish to think about - with only one collision in those too many years.