Family Sharing - Purchase Sharing

Why is it not possible to share my purchases but not my purchase method? Forcing family organizers to share their payment methods with family members seems like a very poor and short sighted implementation of Family Sharing. Instead why not give options within Purchase Sharing to allow the organizer to chose what to share? In my family I am the heavy Apple user, my elderly parents and younger brother only make use of Apple devices for their phones or for Apple TV. I want to share my library of movies, apps, etc. with them without needing to worry about someone accidentally buying a high price item using my payment method. Seriously how is this not something that is possible to share what I have purchased but not force me to also share my payment method?

Honestly can't believe that Apple is not getting massive amounts of negative feedback on this method of sharing where they force family organizers to share payment methods with family members just to allow those family members to watch a movie that the organizer purchased.