Max Contingency
Whilst I agree that there are enough candidates of sufficient quality out there, the ATC helps to attract, encourage and hone those candidates to make their entry into the RAF more likely and smoother.
As an ex- ATC cadet myself, I found that the information and experience gained in the Corps helped me avery great deal during the OASC selection process and IOT at Cranwell.
It is surely a relatively cheap recruitiment and training process that can be paid for by one years Red Arrows travelling expenses (and in my view is much more effective).