"Alex Ignatov \(postgrespro\)" <a.ignatov@postgrespro.ru> writes:
> Why do Postgres have no such functionality as DROP USER CASCADE? Is there
> any reasons in that absence?
The short answer is that DROP USER couldn't reach across databases to get
rid of owned objects in other databases. See
https://www.postgresql.org/docs/9.6/static/role-removal.html
regards, tom lane