Because it seems none of you actually understand Bitcoin. You just repeat narratives about Bitcoin and at the same time ignore what Bitcoin actually is - a database with data on nothing. A database that stimulates real databases. Real databases contain data on some aspect of reality - for example on the number of actual things or about events that occurred. On the other hand, what is put into the Bitcoin database are units of the number 21 million that an anonymous guy created in their imagination. And then people create narratives trying to come up with a thing held by these units. A thing that doesn't exist in reality. It is both comical and tragic to listen to those narratives.
to an extent what you say is true. bitcoin only has value because everyone agrees it has value. or enough people agree. unlike something like gold that has intrinsic value because it has physical uses.
Bitcoin units are abstractions, representation of a number created in Satoshi's imagination. Meaning, they don't have value by definition. They have a price. If I create shares of a non-existent company that I named XYZ and then someone "buys XYZ" what is created is price, also referred to as 'market value'. However value or 'real value' is what actual companies, with assets and liabilities, have. And what actual things such as cows, metals, or debt have. In the Bitcoin system nothing actual exists. Only an abstraction - that number created in Satoshi's imagination. So there's nothing to assign value to. People just transfer units of that number and that's it.
By the way, I see that you compare costs of 'mining gold' to costs of 'mining Bitcoin'. Bitcoin has no costs. There's no such thing as Bitcoin mining. That's just stupid narrative repeated by people. Costs in the bitcoin system refer to a random trial and error of finding a solution to a hash combination. Attributing new Bitcoin units to addresses has zero costs.