The narrative of one person defying the prevailing viewpoint and leading the way to a better world isn't just used because it's a pretty story. It emphasizes and encourages good qualities like critical thinking, creativity, and personal integrity. Consider Galileo, trumpeting the truth about heliocentrism, Columbus bravely sailing away towards what everyone thought was the edge of the flat world, and Darwin going public with a theory that defied creationism.
That's one way to look at it. Most people reading this will know that almost no one in Columbus' time actually believed that the world was flat. The story was made up entirely to fit the exactly this narrative. Galileo did suffer for putting forward a belief that defied the ideas set out by the powerful, but he wasn't the first to do it. Nicolaus Copernicus presented the theory well before Galileo was born, and his version was met with the approval of many, including those within the religious establishment. As for Charles Darwin, evolution was also a well-established idea by the time he was born. Two naturalists, Edward Blyth and Alfred Russel Wallace, even touched on the concepts of natural selection before On the Origin of Species was published.