If you believe there is an autism epidemic and that real autism numbers have been growing, it makes sense to focus on causes.
Autism can be horrible. I could go on and on on the many ways it can be horrible. It might be *ok* (as in : not worthy of changing) for high functioning autistic people, but they are hardly the only people on the spectrum.
Treatment for autism is very problematic. Many therapies are not very effective. Many are very pricey. The best mainstream science thinks we have is ABA which only works for some kids, if it started early enough (which is not the majority of kids) , and it is very pricey.
Prevention, in my mind, hold more possibilities than treatment. Prevention is always better that treatment.
I do not think (at all!) that all resources in autism research should go towards looking for causes, but some should. I think more should go towards looking at environmental causes as very little money is spent looking at environmental causes, despite the fact many scientist do believe there is an environmental component to autism. I also favour environmental causes, because in some ways they seem easier to avoid. Genes are genes and short of not procreating, there is not much you can do….avoiding a anti-depressent in pregnancy is something you can do.