Sure, if it's not doing harm. But in this case, all this old data was really costing us: - real costs - database storage, blob storage, (minor) perf impact

Sure, if it's not doing harm. But in this case, all this old data was really costing us: - real costs - database storage, blob storage, (minor) perf impact - hidden costs - tougher to create test environments that look like production if production is so large, but largely invisible / unusable.