If you ask a Bitcoin investor about why they invested, then they might explain it as a store of value, "digital gold", or etc. With that narrative, Bitcoin makes sense in the world, and isn't just a fad. And the erratic price is just a growing pain, it'll stabilize eventually.

But of course, the real reason many people are buying BTC right now is because of the speculative nature, they want to get rich quick. If someone's investment in BTC is significantly larger than their investment in bonds, commodities, real estate, etc, then "it's a store of value" is probably not the real reason they're buying BTC.