Gold is another store of value, but not that unstable. It reached 2000$ recently and was above 1000$ for many years. Those who invested in gold back in 1900 would have made a great choice since it costed only 20$ back then if I'm not wrong. (Although dollar was way more strong than now)
Bitcoin can lose 500$ within one night. Gold can't. Why that?
There is no point in comparing gold and bitcoin - these are two completely different things. Gold is not even a currency - it is what the currency is backed by. Gold is what gives value for any currency, and accordingly for bitcoin as well. Why doesn't anyone talk about silver or platinum? There are metals much more valuable than gold