Can you imagine a brokerage in the US being able to say that the underlying is 'designed to increase in value' or that it's value 'decreases occasionally'? They couldn't because it would be illegal.
Bitcoin does not represent the assets of any enterprise. Currencies have their value pegged (at some point) by a soverign which Bitcoin doesn't have. Bitcoin is designed to float (which means rise to the top) amongst other currencies. That is axiomatic of the design of cryptocurrency, not merely a prediction.