In this case, I've no doubt you're probably correct. However, the principle remains, and there is no shortage of examples -- not the least of which is strongly religious parents withholding medical assistance for children, sometimes with very devastating results.
I don't think that's a fair comparison to make. While you may have primitive societies with outdated, or even superstitious beliefs, those cannot be compared with the mentally ill, who don't fit within even those outmoded societies.
Consider, as well, exorcisms, which surprisingly are still practices around the world -- even in the United States. (In fact, exorcisms declined steadily in the US from the 1800s until mid 20th century, but increased by about 50% in the 1960s and 1970s.
These are systems of belief reflective of the cultures they revolve around, their worldviews, their systems of reality. We in the modern West have a different system of reality based upon certain philosophical principles which gave rise to Modernity. We should make no mistake however, our system is just as primitive to other systems of understanding as the future unfolds for us through growth.
Exorcisms don't fit within the modernist framework. But they do fit within the magic and mythic frameworks. They have an internal logic to them as they symbolically represent reality to them.
One might expect people in the first century AD to have small knowledge of psychology, and to explain madness as possession by demons, but there is no reason for doing so today, and thus the fact that there are any exorcisms at all shows a continued reliance on irrational and magical thinking.
But this is the 60 million dollar question. Why is it that it persists? Shouldn't everyone be at the modernist level of reality which sees truth through a rationalistic framework of logic based upon the philosophical principle called the law of noncontradiction? Since we think like this, why shouldn't they?
That's a fair question, and one that trips people up at the same time. The reason is, because the researchers who have investigated that very question have mapped these out as stages of growth development. Every person, and every society grows through predictable stages which all have and use different frameworks and modes of cognition to perceive and think about the world. It's not just a matter of sharing knowledge, but actual developmental stages of growth which shifts how one's mind thinks and perceives.
There are various names that can be cited into their supporting research on this, if you're interested.