Historical items are retained in the catalog because they are essential for measuring similarity between users who interacted with those items in the past. Even if an item is no longer active or purchasable, the interaction signal it generated remains a meaningful data point for understanding user preferences and computing user-to-user or item-to-item similarity. Removing historical items from the catalog would degrade the quality of those similarity calculations. Organizations should therefore treat catalog management as a long-term data asset strategy rather than a simple housekeeping task.