1. It is needed for industrial/electronics purposes.
2. It is internationally recognized as being valuable, regardless of culture. That is, cultures as diverse as India, China, England, Russia, pan-Arabic (i.e. non-Jews in the Middle East) have all viewed gold as having value, and that over at least 1000 years of recorded history each.
3. It does not corrode or rot the way paper money does. In Israel they recently found some Byzantine-era gold coins, aside from the obvious numismatic/collector value they still retain value for the gold itself.
4. Gold does not require a government to enforce its value. It's value is innate or intrinsic to the thing itself. As such if a government falls or decides to modify the value of a paper dollar (as Mexico, Argentina etc. have done in the past) then the value changes. Gold that you have in your pocket cannot have its value modified by a government order.