Keith...
I see your logic. Unfortunately I suppose I look it at in a much more black and white way...
I have already been working in the industry, in another country, and have a fairly good idea of the daily requirement for practical knowledge of all things aeronautical. I think for me the ATPL G/S is more something I just want to get over and done with - the other thing that bothers me is that it takes quite a chunk of time and a lot of money (even the GS is pricey) and I don't feel that in my career it will benefit me to any great degree. So, the cost/benefit analysis of 9 months or so of Ground School is negative. If the material was actually relevant (as I have said) then I would enjoy it. I do not, however, see much relevance at all.
An exercise of the mind? Definitely. In itself, a practical use, beneficial to my time? Definitely not.