A bitcoin doesn't create cash, it just becomes more valuable if you find someone else that is willing to pay more for it than you did (i.e. the 'greater fool theory'). This is why it is speculative - i.e. in the absence of it generating revenues, people are just assuming that someone will buy it for more than they did in the future because of scarcity.
Does the US dollar not have value?
However, its actual value is higher because people have decided to use it as money.
Clearly anything that someone is willing to trade for something else has some sort of 'value'.
- value based on intrinsic utility (gold/oil)
- value based on potential future utility (stocks)
- value based on extrinsic utility (USD/coordination)
The issue, of course, is that people disagree which category Bitcoin (and other cryptos) belong to. The other problem is that a singular thing doesn't necessarily only belong to one category. For example, I put gold in the intrinsic category, but it probably belongs in the extrinsic category too, as gold is used as a medium of exchange that is not directly tied to its intrinsic properties, but merely has intrinsic properties that are useful in that regard (fairly scarce, not varnishing, etc).
Maybe it's also useful to separate out the second bullet into:
- value based on potential future [extrinsic] utility
- value based on potential future [intrinsic] utility
There is a difference in buying stocks which have future cash flows that the value is theoretically based on (which are typically generating revenue/profit/dividends because of the business activity) to speculating on forex or bitcoin (where you are just speculating that someone will be willing to pay more than you bought it for in the future).