We live in a world of accretive append-only data stores. Your photos library keeps getting bigger until you die, and then your kids inherit it. Your "app data" lives in the cloud and when you stop using an app it's not clear if it should be deleted or archived. Steam does not (and should not!) delete your saved games for game A just because you aren't playing it right now and have switched over to game B. We all produce an unceasing contrail of data exhaust which we expect to be available.