Yes, and some currencies do lose value because the government and economies backing them have lost trust.
The demand for USD comes from people wanting to do business with one of the biggest economies in the world. The demand for Bitcoin comes from people wanting to make money by hoarding Bitcoins.
It could be different, but right now it is not and I'm not sure if Bitcoin (or any other cryptocoin) would survive a transition to become a currency or something else less like a pyramid scheme.
You're kinda dismissing it without respecting that it's no different from gold as far as people wanting to hoard it. People also do use Bitcoin when convenient to move money. I personally used it to pay someone in Brazil for some mechanical keyboard services when PayPal failed to transfer the money. Totally legal and organic demand exists.
Have you compared the gold price with the Bitcoin price?
I'm not saying it Bitcoin could not be like gold, I'm saying right now it is not and everyone in it doesn't want it to be. And I'm not convinced it ever will be.
I'm thinking in the long long term of hundreds of years. Seems to me when we start exploring space moving around heavy chunks of metal won't be so useful anymore and we'll need to use a Blockchain to verify value transfer.
While I agree we will probably want something different from the current status-quo when light-lag gets big enough to matter for normal daily financial interaction, one potential solution could be to go back to local banks holding money locally, just as things were here on Earth before ATMs and cheap telephony.
We haven't been using heavy chunks of metal as currency for a while without a need for blockchains. I see mostly disadvantages compared to government backed currencies.
The demand for USD comes from people wanting to do business with one of the biggest economies in the world. The demand for Bitcoin comes from people wanting to make money by hoarding Bitcoins.
It could be different, but right now it is not and I'm not sure if Bitcoin (or any other cryptocoin) would survive a transition to become a currency or something else less like a pyramid scheme.