I'm not Mormon but I did live in Utah while in High School for awhile and learned about Mormonism quite a bit. As others have said, it seems to be a personal parent issue; however, Mormons are "typically" considered more conservative in general, therefore it is not difficult to see the parents making a choice like this, in part (even if a small part) due to their religious views. With that said, my neighbor is Catholic and while they don't necessarily go to church every week, she seems to be quite a spiritual person. She has told me her kids are not allowed to do sleep-overs -- at all. The oldest is 11, but she means EVER. In fact, her kids have only ever slept at two of her sisters' houses and I think that was for all of four nights total in their whole lives. So, again, I think it's the parents... unless of course this child has slept over at other people's homes?