If you are a parent and lose a child then you would want every possible avenue taken to find your child. You would be going mad wanting to find them. If there is a way to match photos to known missing children then I say it should be at least tried.
I equate this to Ring cameras. They are everywhere. You cannot go for a walk without showing up on dozens of cameras, which we know Amazon (god mode) and law enforcement abuse their access privileges. However, if a crime happened to you and a Ring camera captured it, then I know almost everyone would certainly want that footage reviewed. Would you ignore the Ring footage possibility just because you despise Ring cameras? Probably not.
It’s all an invasion of privacy until you’re sitting on the other side of the table where you have a vested interest in getting access to the information.