Dollars don't provide any what you call 'direct service' (if you don't use them as a wall paper that is), or 'use value' (in Marks terms I think), they only value is 'exchange value'.
Dollars, like all other fiat money, originated as a commodity backed currency, either with direct backing of a commodity, or indirect backing of a commodity by being backed by another currency that originated as a commodity backed currency. Bitcoin is not a commodity in itself (only directly serviceable goods can become a commodity), and has no direct or indirect commodity backing it.
It is possible that money started as commodity - but the point is that what differentiates money from commodity is that it has much higher 'exchange value' then 'use value'. This is really what defines money - so when you have something that has only exchange value and no use value - then it is kind of 'pure money'.
I'm willing to trade all kinds of umarketable, worthless shi...err, I mean "pure money" for your real money.
Money can only emerge in an economy if it is first a directly serviceable good. If something provides no direct service to anyone (meaning it does not provide a direct means to
anyone's desired ends, and is therefore not valued by
anyone), why would anyone buy it? If people realize that it provides no direct service to anyone, and therefore has no value to anyone, and no one is willing to give up something they do value in exchange for it, how could it ever emerge as a money? What business would accept it? What person would accept it as a salary? Social contract based "pure money", metaphorical goods, etc., only have exchange value when there are people buying them that do not fully understand what it is that they are buying.
Bitcoin is, and always has been a bubble. It's price is disconnected from the reality that it is not a directly serviceable good.