Here and elsewhere I read repeatedly where CAMHS question someone's parenting skills rather than actually assess the child in question. One of my favourite quotes has always been along the lines "unusual parenting of a child with ASD is not the cause but a parents' response to their own child's particular needs"
My parenting has never been brought into question probably because the autism was and still is blatantly obvious and I have managed to avoid CAMHS but behind closed doors I'm sure the powers that be would have a field day if they ever witnessed how I actually parent 
I assume part of the reason will be that parenting courses however ineffective are far cheaper than a diagnosis and proper support but at what cost to families? 