I grew up with the same social norm. But rather than seeing it as a calculation to prevent change, I always assumed the reason was simply a strict deference to the idea of religious tolerance. We didn't ask questions because questions could imply criticism, which could imply intolerance. After all, many of the first European settlers to North America came here to escape religious persecution. So it makes sense that their descendants would go a long way to avoid anything that might resemble religious intolerance.

But regardless of the reason, I do agree that it prevents idea exchange. I grew up Presbyterian, and when I was a kid, I actually had a similar incident with a Mormon friend. She had taken a trip to Utah for her older sister's wedding, and she said she was a little sad because she didn't get to witness the ceremony, because she was too young to enter the temple. But she said she was still happy though, because the fact that her sister got to marry in that temple meant that she would get to remain with her husband when she died - which she wouldn't have been able to do otherwise.

I told my friend that that's not how it worked, and she said "well that's what I believe". I then realized that it was a religious belief, and so I quickly apologized and shut up. So we continued to live in our little bubbles - not challenging each other's beliefs, but also not learning anything.