It has nothing to do with science. It has nothing to do with learning. If you assume it's just a bunch of uneducated hicks refusing to participate, you, too, are not doing science. That's bad math.

Many people not choosing are very well educated. There is very good evidence for the US government lying, manipulating information, and in the past having done experiments on the US population without it's consent. Tuskegee. Radiation. Has there been a science that has not been politicized and economized? Environmental science? Fauci actually waffled on masks 3 times. Masks work, absolutely. No body is talking about how Flu rates were significantly decreased through the Flu season. Probably because of masks and social distancing. There is evidence corporations have lied, manipulated economic structures, and done experiments on people, and their employees. Radium Girls, led paints, Erin Brockovich. Bottom line, you can't have a history of lying and then expect people to believe you, "Just this once... we mean you no harm."

That alone is enough to put doubt in people, but we haven't even begun to discuss sociological and psychological motivation, and this, too, is science, and might explain why people might be reluctant to participate in system that have failed to secure a nation's trust.

I am really not sure why you ask why. We have this idea of freedom and individual choice. If someone lists a reason for not taking it, you can debate. All of the science you brought here, good science. But when a person says, "I don't want it." There is no more debate. People don't want it, the state need to back off. It's a country for the people by the people, and anything else, well... that usually riles people up. And this brings us into another science, the dance between individualism versus socialism. They both have merits. It's probably a continuum. There is probably a balance, with this thin line where we get the best of both worlds. We are on that line now, in dialogue... That, too, is what it means to be a free nation.