There's a second order effect IMO: people put specialized resources into mining it. Thus people have a sunk cost. In general, people also have a sunk cost fallacy which means that the sunk cost will stay into the object/subject it was sunk in.

Due to the sunk cost fallacy, Bitcoin has more value. I know this means I'm relying on the irrationality of humans, but why wouldn't I? It's more predictive than assuming humans will be rational with regards to this subject.