I believe this would sum up the answer to that good question very well...
In other words, even family & friends will have the one bad apple that will burn up too much data (slowing it down for everyone else) or make a bunch of international calls at added cost but be slow to pay, etc. Friendships and even family bonds can break over money matters.
And much like Netflix putting the pinch on sharing access in different households, if the goal IS to extract about $115 per household, I would guess that mass embrace of a friends & family pool at many addresses would lead the cell phone providers to implement the same IF it cut into maintaining and/or growing the average.
IMO again: best option to all of these "new plans" that all revolve around extracting about $100-$130 per household is "just say no." MVNOs are generally using the same networks, the same towers, the same 5G, etc but can cost considerably less than the "big 3."