Sidecar needs to be added to Family Sharing

There are many posts even back from 2019 from disappointed users who may have a family iPad connected to Family Sharing but are unable to use it for Sidecar feature with their Mac.

I am one of those users, have the iPad in front of me and will have to log out my daughters Apple ID add mine just to use the feature for an hour.

Come on Apple these are blatantly obvious simple features that should have worked from the start! Or is there a reason why they could but don't ;)