How does that differ to investing in fine art, scarce wine, old/rare stamps and coins, limited edition/novelty items, historical artefacts, or even gold?
There's loads of things that have kept value for centuries despite having no intrinsic value.
Not saying Bitcoin is worthless; it's a currency and it has it's uses, which makes it worth something. However, I think the belief that "it's scarce, therefore its worth something" is a false one and leads a lot of people to speculate wildly on it.
That's not the argument being made. My paintings are scarce but they're worthless. Lots and lots of scarce things are worthless, and rightfully so.
"bring people some measure of joy."
Right, so there's some aesthetic value there. Why can't BTC be like the Ancient Egyptian artefact that's valued purely on aesthetic grounds? I could plausibly see it as a historical artefact in 200 years time, given its novelty and role in tech history. I have an old stamp collection and some BTC, and I get much more pleasure from the crypto due to its novelty, role in culture, etc.
BTC's value now could come from it acting as a store of value for example. Or its value could come from the novelty aspect. Or that it facilitates online gambling (leveraged bets on crypto exchanges) in countries where such activity is heavily restricted. BTC's value in the future could come from it being a historical artefact. Lots of subjective reasons investors may have for holding it (just like they hold a piece of art) beyond its use as a currency.
However, I wouldn't accept bitcoin as a method of payment because I'm not confident that people will agree to a completely different value in a very short time frame. Meaning will it be 50k next week? 5k? Who knows!