is backing up a live postgres enough?

I recently restored a debian system from off-site rsync'ed copie of
/{var,etc,home} including a large Postgres db in /var/lib/postgres/data.
FWIW the rsync backup was run nightly on the _live_ system with all
daemons active.

The db started fine on the restored filesystem. Was I lucky? Is it still
necessary to create a daily dump with pg_dump? What is the accepted
practice w.r.t Postgres backups?

Thanks in advance, cheers,

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