any system of record has a requirement to be bitemporal, it just isn't discovered until too late IME. I don't know if there's a system anywhere which conciously decided to not be bitemporal during initial design.
It will hopefully be in PostgreSQL 18.
Is there an active effort to get temporal tables into Postgres at the moment?
It looks like Paul A. Jungwirth and others are trying to get Temporal Tables into Postgres 18.