In my personal oppinion, because a lots of people using gold as somewhat "based for trading".
A preasure from technology site can change people as well.
International space station, long space exploration etc. that can result in finding another stuff more effective than "gold" ?
Or antimatter research like giant atom smasher... that can result in convert things by atom bases or unknown result ?
A "based for trading" won't always keep up with future technology... ,
can't keep up with human population... it will changed... but it needs process and or replacement...
And i hope it won't results in another WW,
while bitcoins is somewhat based on electricity... and technology ?
so a country with more electricity and advance in technology will have more power ?
that is why i don't know about the future of gold...
personally I'm scared using gold "as a place to run off" for all my fortune.
What if some CERN scientist saying that... "We can create gold" ?
Well that is my personall opinion