That is how you know this physical existence is not exactly natural as everything ages and dies. This world is not all that because it is impermanent. Of course GOD wanted it so but why...? Why would GOD cover a part of creation in physicality ?
We have to take into consideration another part of GOD's creation called the angels who live forever. One angel in particular caused our first parents to not only disobey GOD but to doubt GOD's truthfulness. It's like a mother telling her child not to touch a hot cooking plate because it will burn and hurt. And then a big brother comes along and tells the child not so it will not hurt...
The angels are an active part of GOD's creation and are allowed to watch over and help humans and some angels even sired children with women (which was not allowed) human angelic hybrids known as the heroes of old who became spirits or daemons when they died.
So our world got a big spirit problem ! GOD is watching and letting it all play out to see and test our individual and collective character... who will we be ?
Will we revel in evil or try to be good ? Will we pursue truth or sex drugs and rocknroll ? Who will we be ? That is our choice !
We are free to be whatever we want... but don't hope to be with GOD forever when we cannot be bothered about truth and goodness !