There is I suppose a comprison to the decline of University Air Squadrons
And we should not forget that the original idea of UASs was NOT as a recruitment tool - if you wanted to join for a career you went to Cranwell.
Trenchard's idea was to expose the future "movers and shakers" of this country (fewer than 5% then went to Uni) to the ways and ideas of the fledgling RAF. Similar argument holds for Air Cadets - the more important alumni of both organisations are - IMHO - those who don't join but know about us.