Yet people aren't doing it? Why?
Great question.
IMO, one reason could be some people are always on the look out for a reason why bad things happen.
They want to know why their children develop autism. Why my nephew is diabetic.
They want something to blame to make it easier on them. That way, they can feed their anger into a cause of some sort.
When the truth may be that we just don't know.
Now, the best way we know how to go from not knowing to knowing with some degree of certainty is science and it's practices. We've been using it for centuries with pretty good success.
You couple wanting to know the reason with the fear of screwing up your kids and you have a compelling case for for some parents not to vaccinate.
IMO, what they need to be looking at is potentially bigger effect on the spread of disease throughout the US and\or World versus the chance that someday your kid might develop a disorder. Never mind the fact that we have no reason to believe that one causes the other.
The spread of disease is something that's pretty certain to happen if the level of un-vaccinated people goes up over time.
We've been there. That's how we got here. It was bad, we came up with a pretty effective way to stop these diseases and it actually does work. That's how we rid the world of smallpox, the only disease to be eradicated.
What doesn't work is not vaccinating your kids in the hopes that they won't develop some sort of disorder.