Yes. We get more questions on those two exact things. Sun exposure and PWS and heredity and birthmarks.
I will agree that there are a few (but very few) parents who cover their child's PWS, but it is mostly because they get tired of dealing with the stares and rude comments from others. It isn't because they are afraid of being judged for having a child who looks different. It's because they need to get an errand done without having some a$$hole break their hearts with some stupid comment.
Those people who ask about having another child with a birthmark have every right to be concerned. Those parents have valid health, family, and financial concerns. We (meaning my husband and I) have a child with a disability. It is not proven one way or the other that this disability is genetic. We are scared to have more kids. Why? We are struggling now to pay for treatments. We have a valid financial concern when it comes to a family issue like that.
No one knows what might happen in getting PWS treated or not, you're right. But a responsible parent weighs the options and makes an informed decision and that is what we try to help with. As I said, those parents who don't struggle with that are not here... they don't need our help or support.