I bet you wish you hadn't spent those hundreds of bitcoin, don't you?
As I said in the last post I linked, Bitcoin handles a few billion dollars a year in cross-border remittances, largely to family members in Venezuela; this suggests that it's keeping several million people alive. I hear there are still darknet markets around, too. So there are current uses as a genuine medium of exchange that are very significant.
Do they amount to its primary use? I don't know. I suspect Bitcoin's primary use right now is speculation, and I wish that would settle down, because I'd really appreciate it if the money I get paid in would retain roughly the same value for weeks at a time. But perhaps the primary use of US$100 bills is cocaine trafficking; if so, what does it matter to people who are using them for other things? If the primary use of oxygen were feeding pathogenic bacteria, would you stop using oxygen?
I don't think it's a problem that Bitcoin doesn't contain its own fraud or contract dispute resolution mechanisms. Neither do gold, silver, copper, or greenbacks, and they work pretty well as currencies. Last time I had a dispute about a Bitcoin transaction, I resolved it by negotiating with the person I was disputing with to find a mutually agreeable settlement, which took about an hour; failing that, theoretically I could have resorted to talking to their friends, the Mafia, or, yes, the police, but probably I would have just swallowed my losses and not done business with them again. (In theory I could also have resorted to individual violence, too, which is probably the most common dispute resolution mechanism after simple negotiation.)
You may or may not be aware of this, but commerce is enormously older than states are, perhaps by a factor of ten, and a great deal of it has been conducted throughout history outside the aegis of any shared authority to whom disputes could plausibly be referred. It's true that a good dispute resolution mechanism reduces the risks of commerce, but commerce is often still worthwhile without it. Ask anybody who's worked under the table, been an illegal immigrant, rented a room illegally, or bought drugs on the street.
I'm not railing against government systems in this thread. They have their good points and their bad points. Fundamentally, though, I think history has proven out Lord Acton's maxim that power corrupts, and absolute power corrupts absolutely; and, because I have seen the devastation corrupt governments can wreak, I do not think that governments should have absolute power.
I especially do not think the US government should have absolute power over Russians, or that the Chinese government should have absolute power over Americans; the history of such arrangements is replete with avoidable famines and intentional genocides.