When you put money into blackjack you're not buying an asset. A crypto coin is an asset that can be held. Just like a share of a company, or a dollar itself.
I can imagine a lottery where usually nobody wins anything but every now and then everyone who bought a ticket wins collectively. It's still a lottery.
With stocks, for example, I can make a prediction about a company's future performance, buy or short accordingly, and expect that if I am correct I will profit.
I may be wrong about my prediction, but if I am correct then I've got far better than chance odds of also being correct about the future price of the asset.
Without making any further predictions about the state of the world I can equally easily imagine the price of Bitcoin in 5 years being $100 or $100,000. Neither price feels "wrong" the way it would if, say, Google's stock price rose or dropped by an order of magnitude without the company changing anything.
With other assets, there's a clear causal arrow leading from outside the system back in. If Google the company performs better, Google the stock will overwhelmingly tend to perform better. If Google the company folds, Google the stock will overwhelmingly tend toward being worthless. The asset is a proxy for something that isn't the asset.
Bitcoin doesn't appear to work the same way. There's no obvious not-Bitcoin that demand for Bitcoin is a function of. It's a proxy for itself, after a fashion. That doesn't mean it has no value, but it does feel uncomfortably self-referential when compared to almost any traditional asset class.