The quickest way to ship a family app is one account with a shared password. Everyone logs in as "the house". It works for about a month, until you want to know who marked the trash as done, or until a teenager needs the calendar but not the mortgage paperwork.
Attribution is not surveillance
When every member has their own account, a completed chore has a name on it, an event has an owner, and a list edit is attributable. That is not about monitoring anyone. It is the difference between "someone said they would do it" and knowing the thing is handled.
It also means the app can show each person their own day rather than the union of everybody's day, which is the difference between a schedule you scan and a schedule you ignore.
And roles can differ
A household is not a flat organization. Adults administer it; kids live in it. With separate accounts, a child can have a real presence — their events, their chores, their allowance — without inheriting access to the lending ledger or the document vault. A shared login cannot make that distinction, so it never does.