TL;DR: Immutable backups stop deleted files from ever being purged, giving you a true last line of defence against data loss. Immutable backups keep deleted files indefinitely instead of removing them after the standard 28-day retention window They protect against accidental mass deletion, ransomware, and compromised accounts wiping live data Storage grows over time since nothing is purged, so costs rise gradually with volume A review of what's actually being backed up helps keep retention policies sensible rather than backing up everything by default ...