You seem to miss the point. Yes if you want to hide things from your family or friends it is a useful tool but many people do not want to do that. They have open relationships and do not want to create conflict by being presumed to have something to hide.
Such conflict can lead to domestic violence and make people, particularly females, feel unsafe.
Likewise, parents will also not be able to monitor their children’s activities and in this corrupt day and age of on-line grooming having apps that are hidden means that they may not be able to keep their children safe.
I see nothing wrong with having the app should one wish to hide things from their family but I think it would be better if the folder could be switched off and removed for those of us that have nothing to hide