LJ:-
It made me question why we bothered we UAS. However, having now read the line about it being Trenchard's plan in giving RAF experience to the great and good who wouldn't join the military but would go on to be politicians, financial gurus, businessmen, doctors, etc...
No doubt Trenchard had the right idea when being "air minded" was both very new and very challenging for those who would end up "running things". Since then you would be hard put to find someone today who hadn't savoured of the thrill of endless queues and delays at airports and had air very much in their minds, though not I grant in wholly positive ways.
As to saying no to the likes of the OP's son hankering to join a UAS, it strikes me as a very aloof response to say, "No thanks, you're too keen, we only spend money on those that aren't". As I inferred in my previous post, it smacks of the way that discounts, cashbacks, and reductions, only go to new business customers, the loyalty of the old ones being heavily penalised. If I can learn to be a perpetual new customer, I'm damn sure that the bright young things already have!
The OP says that his son will grin and bear it. Good man! Others though might take umbrage, and find a more welcoming institution. As the OP asks, what is the point?
Strikes me anyway that a JOTC (or UCCF? :-) in place of the three separate offerings might save Johnny Taxpayer and/or the Services some money, as well as promoting the purpleness that now colours all that is defence.