The value of Bitcoin does not come from some arbitrary value, and therefore people trade it. It’s quite the opposite: because anyone can trade with BTC (anywhere, everywhere with no fraud and very low fees), that as a result it has value.
With bitcoin, we can trust the people, not one man. We can trust that 51% of us are honest. We can trust that we, collectively, can make the best decisions where our own money is concerned and not one faceless bureaucrat. We can trust that the same rules apply to all.
It is a mistake to think that the BTC gets its value from the energy needed to manufacture it. Cost is not value. A thousand men can make a hole in the ground at a cost, but that’s not worth anything. Scarcity is not a source of value either: fingerprints are scarce but not valuable.