It's a prisoner's dilemma. If you want people to vote away the government what you need is some way to communicate intentions about voting with some assurance that people will do what they say they will do.
The opportunity cost may be small but the benefit is also small. The benefit is a tiny chance of affecting the outcome (or no chance given the way the USA works now).
The opportunity cost of voting is something good you control that directly improves your life. Only the more easily manipulated people will be convinced to vote instead. The decisions of democracy are biased toward people who are easily manipulated.
Yeah well we have to actually build it and for the longest time I couldn't find anybody who thinks epistemology is important enough! The quicker we actually do this the fewer people die.
The truth allows you to reduce risk for yourself and if you tell the truth to others than society will be a less risky place to be. That's why you can be more risky and boost the truth higher if you know what it is.
No, it is not possible to know what is going on with very much certainty because there is so much deception. With Boost we could have collaborative truth-seeking and then we'd all know.