A middle ground between individual and fully shared
A household account groups a small number of semi-trusted people — family, housemates — under one shared subscription or resource, while still distinguishing each member through a distinct profile and, often, a distinct level of access. This differs meaningfully from a fully individual account, which assumes exactly one person, and from full account-sharing, which collapses everyone into one undifferentiated identity with no way to distinguish who did what.
The design challenge is specific to this in-between case: members genuinely are trusted enough to share the underlying resource — a subscription, a family plan — but not necessarily trusted equally with every capability the account as a whole makes available, which a design built around either extreme doesn't have a ready template to handle.
Profile switching has to actually enforce the boundaries it implies
Profile switching lets someone move between distinct profiles within the shared account without a full re-login each time, which is what makes the arrangement practical day to day. Its value depends entirely on each profile's own data and settings staying genuinely separated — a switch that's fast and convenient is only a real benefit if it doesn't also make it just as fast and convenient to reach a different profile's own information than it should be. A household structure with weak boundaries between profiles ends up functionally indistinguishable from full, undifferentiated sharing, just with a friendlier interface suggesting distinctions that aren't actually enforced underneath.