Are there things that you "just don't want to know"?

Here is the background. I have some friends and she is expecting their first baby. They went to get an ultrasound but when the opportunity arose to know the gender of the baby, they (actually she) declined to find out. She thought that they should be surprised.

(Please skip comments about where the guy’s opinion fits in here. His opinion never matters. That is another question.)

Anyway, it is their business, and I would NEVER say anything to them about it, but…
I think that is silly.

How can a thinking creature, like a human being, not want to know something if in fact the knowledge is availabe to them? Isn’t evasion of this sort bordering on immoral?

But maybe it just depends on what it is that you do not want to know.

What knowledge that was available to you would you “just not want to know”?