But the system that the node is upholding is not altruistic. When you opt-in to the Bitcoin ledger, you're agreeing to play by rules that are based on merit and individual achievement. I could see why the single act of running a node could be considered altruistic in isolation, but it exists in the context of a network that has zero tolerance for freeloading (that is, you can't acquire Bitcoin unless you work, or someone who does work voluntarily gives it to you). The benefits to society are a secondary side effect, whereas democracies explicitly demand that people work for the benefit of others for nothing in return.