See where the puck is going. Bitcoin goes to more and more hands. It can stabilize only when everyone who might want it, knows about it and has some of it. By that time BTC price will be 1000x higher than today, that's why many are rushing in to get it while it does not cost millions.
Secondly, only very recent investors may worry about volatility. Everyone who bought in 1 or more ago don't care about volatility. All fluctuations are well above their nice profit and they can spend 1% of their stash comfortably, knowing that the remaining 99% are growing in value faster that the stash is being depleted. Today's investors would have to wait another month or year before they also get 10x return and won't worry about volatility.
"Store of value" works pretty well when your value not only stays the same, but increases over time. 10% jumps do not matter if you have 10x more than a year ago.