A household is several people signing up independently over several years. Someone started a music subscription in university and never moved onto the family plan. Someone else pays for extra phone storage on their own account. Each decision was sensible on its own, and nobody has ever seen all of them written down together.
The charges are split across accounts. Some bill through the App Store, some through Google Play, some directly to a card, some to a PayPal balance. There is no single screen that lists them, which is why the total is almost always higher than anyone guesses.
Family plans only save money if people move. Upgrading to a family tier while an individual plan keeps billing means paying more, not less. This is the most common and most expensive household duplicate, and it can run for years.
Nobody owns the review. Household bills get checked when something feels wrong. Subscriptions never feel wrong - each charge is small and each one was, at some point, wanted.