Talk:The Hourglass/@comment-5782071-20150516222115/@comment-28584561-20150517074446

As with Steven's case, the object is a powerful, and I mean powerful, item. It plays dangerously around with the "Many-worlds interpretation (MWI)", the interpretation states that all possibilities that can and will occur has or will happen indefinitely somewhere in another dimension/world. Long story short, if Gems go back to the past and rewrite its history, there is a possiblity (thanks to the MWI) that another set of Gems comes in and stops them, and another set of the initial Gems comes in and tries to stop the Gems that are preventing the tamper of earth's history, it will just go on and on, it will not stop unless the item is destroyed, which Steven had to learn the hard way.

The Gems know that with the item in hand, absolutes are non existent. Their defeat or win could mean nothing if someone uses the item. So they probably chose to not tamper with it as they might cause the destruction of themselves or the universe altogether.