It should be very easy to merge accounts. Even a naive implementation could just modify references from account_you_dont_care_about (A1) to account_you_want_to_be_primary (A2) and then delete A2.
Such a burden on the everyday consumer. Extremely, extremely frustrating. I understand why my parents and others in their generation feel confused by some nuances, because this is just a non-transparent, de-prioritized product goal that will never be improved. I hope we legislate this as part of the Right to Repair plan, it's adjacent.