pg_dumpall restore question

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

I'm doing postgresql backups with pg_dumpall.
When I restore them, all the guides on the net say to just use

     psql -f backupfile

but when I do that as pgsql user on NetBSD, I get

     psql: error: FATAL:  database "pgsql" does not exist

and my workaround was to do

     psql -d postgres -f backupfile

instead. Why is that necessary?
 Thomas