I mean that people only tend to sue parties that have substantial assets. You can't get blood from a stone. Autism treatments (like ABA) are very expensive ($50K/year). Desperate parents are willing to look in any direction to find a culpable party that "caused" their child's autism; a pharmaceutical company seems like an inviting target--if you can afford to bring a lawsuit. If the pharmaceutical company settles, you now have your ABA paid for, and there is the scent of vulnerability and guilt in the air, so others will come forward and try the same thing.
As parents of a sincerely autistic son, we gave up hope a while back, but I can see where some parents would want this to be true.
Are these $50K treatments effective? Can autism be treated without knowing the cause?