It's important to keep in mind the difference between the tangible and intangible. Gold is obviously a good store of value because it is a tangible object with utility value, aesthetic value, etc etc. nobody argues that gold is an adequate safe haven / store of value; the price of most commodities and goods, when prices in milligrams or grams of gold, generally go down with time.
Bitcoin and government currencies that are not backed by gold (insofar as they are used as money) are intangible (ignoring, of course, the physical paper of the bills themselves). In the absence of modern computing technology, gold is the only safe haven in which to store ones wealth. But, of course, modern computing technology is not going away any time soon; it will only get faster, better.
Why is Bitcoin a superior safe haven to the US dollar? The answer, to me, is simple: US dollars can be devalued by increasing the money supply. After the Fed increases interest rates enough to cause a stock market crash, they will start QE 4 and pump trillions of new US dollars into the economy, effectively devaluing the labor required to earn your dollars. Nobody can do that to Bitcoin. If somebody attempts to change the code in order to change the limit of 21 million coins, then my understanding is that that will constitute a software hard fork, and the new coin will operate independently of Bitcoin.
Additionally, the security technology of Bitcoin is far superior to the technology employed by modern banks. I am quite sure that, e.g. in the interest of national security, a person's financial assets stored in a bank can be wiped clean. Set to zero. This kind of action is literally impossible with Bitcoin.