I'm not so sure Strafer.
I think a large part of the problem is the disillusionment that sets in once the new PPL-holder realises that his/her dream of freely roaming the British skies is a myth put about by greedy flying clubs. (Sometimes I think this sets in pre-test - which accounts for some of the drop out rate IMHO.)
I don't think I was unusual when I started this flying lark to dream that one day (wallet permitting) I would be able to fly places instead of drive to them. It's quite a kick in the teeth (no comments please) to wake up to the fact that 7 times out of 10 that will not be feasible due weather, aircraft availability, or prohibitive landing fees.
I know that, because I'm not interested in aeros or the engineering side of things, I have to go on to do the IMC now in order to keep my interest alive.
Which brings us nicely back to That Book. One problem I have with it is that the author expounds constantly pushing one's limits as a method of keeping things going, but is quite scathing about the value of the IMC rating. I cannot reconcile these apparently opposing points of view.