Do they really? I don't think the dead have any expectations at all let alone the expectation of privacy. But also, she was a minor and therefore no real privacy rights with respect to her parents.

Why are they buried with clothes on, often in a literal black box? Their possessions are generally controlled by an executor, privately. The dead expect, again literally, their will to be followed.

Of course the dead expect nothing. But the living expect that their wills will be respected after they are gone. To preserve confidence, we must (make a show of) respect the dead.

One would hope that whatever we leave behind when we die gets treated with some dignity.