Gold (jewelry, beauty that not everybody can have, nowadays industry), silver (jewelry, beauty, industry)
Based on your arguments, do Gold/Silver coins only have value as money if I own a smelter in my backyard (to create jewelry) or if I have a computer parts factory which needs the metal? Would you agree these coins have value (according to your argument) because
other people see them as having value (presumably those with a smelter / factory)?
If that stretch can be made, then it doesn't take long to see why bitcoins have value: trust.
With a tally stick, a bar of gold (tungstun?), a shell, a stone with a whole in it, the paper in my wallet, etc... the challenge is trust. How can I trust you gave me the real thing this community agrees upon as a store of value? What if you gave me a bogus tally stick (I'd have to check with the king)? What if you gave me a different (more common) shell which isn't used on this island as money at all? What if the government is debasing the paper you just gave me so hyperinflation is around the corner (with no option of recovery... see Argentina)?
Via cryptography and the ability to prove (via the Bitcoin network) ownership and authenticity, bitcoins solve the issue of trust. That, to me, is a really big deal. Not only an amazing and useful form of money, but a way to take control away from central banking controls and give it back to individuals.
If governments and financial institutions were trust worthy, the value of Bitcoin wouldn't be so obvious. As it is today, those paying attention understand how corrupt the current systems are.
Is Bitcoin the best there ever will be? Probably not, but I do think it's a huge step in the right direction.