People are willing to give something up for proof of effort; a personal union, or something else of value.
Whenever someone tells me bitcoin is a scam and has no intrinsic value, I ask them about diamonds, expensive art, etc. Most people cannot reconcile bitcoin and diamonds (as jewelery) in the same value frame.
Diamonds do have some functional uses of course, as does gold. But their price is wholly determined by the belief (whether justified or not) that they cannot easily be manufactured on demand. Just like bitcoin.