Gold is not just a store of value, some also consider it an investment opportunity. I'll explain how I find these two different. A store of value is something you can have something valuable in and then expect it to be more or less of the same value after some time passes. When investing money, however, you don't expect to have the same amount in the future, you want to have more, to make a profit. And I think that gold is a great store of value because it's fairly stable and low-risk. Bitcoin, on the other hand, seems like a way better investment, but it involves higher risks. So my point is that if you have $15k, and you want to save this money for your future adult children, gold might be a good option. If you want $15k, and you are willing to risk for the chance of having $150k in the future, then Bitcoin seems more suitable.
I agree, gold is currently less volatile and more stable that BTC. This is partly because it has a much higher market cap.
Bitcoin is still very early, but I believe in the future when Bitcoin's market cap is much higher, the volatility will be reduced.
Once this happens, the only advantage that Gold has, is its application and tangibility. Bitcoin is superior in almost every other aspect.