Gold at least has some unique purposes besides a store of value. Over half of it is used for jewelry and commercial reasons, so at worst it can be considered an over-speculated commodity. Bitcoin literally has nothing going for it besides being the current market leader.
If the International perception of gold being valuable disappeared overnight (which... yeah, won't happen unless someone discovers legit alchemy magic) the difference between losing 90% of your value or 100% if it had no use outside of the speculation shouldn't be influencing almost anyones decision in what to invest in. All the other parameters (volatility, profitability, etc) are way more important than if you are completely bankrupt or completely fucked if the market implodes.
My point is that gold can never lose 90% of its value because the majority of it is already used in luxury items and electronics. At worst, the total value of gold can only drop by the current amount that is being held in reserve or as investments.
Price is set at the margin. If half the demand for gold evaporated the price for gold would likely drop a lot more than 50%, probably more than 90%. When demand for gasoline went up by 2%, the price doubled.
