I have an adopted friend who has no interest in knowing who his bio parents are, either... but there are many people who feel differently and would like to know.

Personally, I would not appreciate it if my parents said, "honey, we are going to give you some very important information about you, info that could possibly affect your mental health and the physical health of your future children. But you may do nothing with this information except keep it inside because we aren't strong enough to deal with what you might do with it".

Of course, they most likely didn't use those words, but that is essentially what they said... we aren't strong enough in our own selves to honor your personhood, instead, you have to be strong so we don't have to grow and deal with uncomfortable feelings.