There are certain powerful artifacts that need to be hidden from the human eye and this is something that has always been this way. The problem is that there is not a single human being out there who is truly ready to do what needs to be done with such artifacts. They would use them for purposes of power struggles and control. The true nature of humans is to be in control of their environment and this is the reason why we cannot trust them with any kind of special artifacts that could be potentially dangerous.
We have concealed quite a large number of important items that will be kept hidden for as long as humanity continues to evolve into a life form that is capable of using resources to make something better out of their world. Currently all that humanity does is make in order to make money or service the cause of making money.