There are people who want untraceable forms of currency. Whether they want it for benign reasons (don’t want a spouse seeing cash withdrawals, credit card charges, Venmo payments) or for nefarious reasons (crypto is now fueling illegal arms sales, human trafficking, child pornography), they want something with a veil of privacy. The Dark Web is filled with vendors selling pretty much anything (industrial quantities of fentanyl, for example) and Bitcoin or similar is how you pay for it.
Any type of asset is vulnerable to speculative investment- Tulip bulbs being a notable example from history.