Parental Bias and Autism

We often get posts on the form asking for advice with autistic children. And I can't help but notice the requests overwhelmingly relate to low functioning autistic children. As someone who is quite high functioning and had a very disrupted and turbulent childhood I can guarantee you it's not because high functioning autistic children don't have just as many issues. Nore is it that high functioning autistic children are particularly rare. We recently had a discussion on this point in another thread and figures I dug up indicated around 40%+ of autistic children being diagnosed these days are of average or above average intelligence.

So the question I'm asking is this. Why don't those parents come looking for help? Is it because the main stream schooling and support systems are so much better at supporting high functioning children? I doubt it. Is it because they tend to think of their child’s behaviour as 'naughty' not 'autistic?' Is it maybe they don't accept or agree with their child’s diagnosis? What do you think it is?

More to the point:

1. How can high functioning autistic children get the help they need if their own parents won't seek it on their behalf?
2. How can we raise awareness of the needs of high functioning children among parents and professionals?

Edit ps: For the simplification of this entire discussion and to avoid a long drawnout arguments over semantics. Instead of high functioning we shall say high IQ meaning an IQ of 85+ and instead of low functioning we will say low IQ meaning an IQ less than 85. As measured on a standard clinically approved IQ test.