A dollar has value because dollars are in demand. A bitcoin has value because bitcoins are in demand. Same thing. Economically speaking it doesn't matter why

A dollar has value because dollars are in demand. A bitcoin has value because bitcoins are in demand. Same thing. Economically speaking it doesn't matter why people demand them (eg. to pay a merchant or to pay taxes). The demand in and of itself is what gives them value. I would then argue that technically Bitcoin is fiat currency.