They looking for a commodity that cannot be manipulated by governments. It should derive it's true value from supply and demand.

The protocol was written to have the same characteristics as gold :

1. It's scarse / rare due to it's limited supply.
2. It has to be mined
3. It cannot be manipulated by governments.
4. It will stand the test of time.
5. It can beat inflation
6. It can be used as a currency

We can go on and on..... yes it's not a physical commodity like gold, but it's created to have the same features.