What is the purpose of expiring snapshots in an Apache Iceberg table?

Snapshot expiry removes metadata for snapshots older than a retention threshold and deletes any data files referenced only by those expired snapshots; reclaiming object storage space consumed by old or unreferenced files. The incorrect options ("To roll back the table to an earlier version after a failed ETL job", "To promote a Silver-layer table to the Gold layer in the medallion architecture", "To convert an Iceberg v1 table format to Iceberg v2 format") are distractors that don't fully capture the concept described.