Those factors affect a bitcoin’s exchange value: for the purpose of exchange, a bitcoin is arguably more valuable than, say, an original haiku. But the difficulty in double-spending bitcoins is irrelevant if there is nothing to spend one on in the first place.
(On the flip side, there are things whose use-value exceeds their exchange-value. If, for example, I am hungry and I have one fresh fish, I would derive benefit from cooking the fish and eating it, but if I’m not standing in a fish market, it’s probably not worth the effort for me to sell it.)
The overall bitcoin protocol has some use-value: even if people stopped trading bitcoins, the protocol for running the system would be a worthy object of study for cryptologists. But you can derive that kind of benefit from the protocol without owning a single bitcoin.
If we can agree that the protocol has value, then the only question is whether or not an individual bitcoin exists outside the protocol. I'd argue it doesn't. You can't point to a sequence of bytes and say "that's a bitcoin".
Instead, a bitcoin exists only as an agreement between the CPU-majority in the network. They agree that user A solved a block, and therefore is entitled to new coins, and they agree that user A transferred that coin to user B, and so forth. But there's no piece of data that specifically represents a bitcoin. Outside of the bitcoin network, bitcoins don't exist, and therefore it's meaningless to talk about them in isolation.
(On the flip side, there are things whose use-value exceeds their exchange-value. If, for example, I am hungry and I have one fresh fish, I would derive benefit from cooking the fish and eating it, but if I’m not standing in a fish market, it’s probably not worth the effort for me to sell it.)
The overall bitcoin protocol has some use-value: even if people stopped trading bitcoins, the protocol for running the system would be a worthy object of study for cryptologists. But you can derive that kind of benefit from the protocol without owning a single bitcoin.