because almost all past and current innovation to make the world a better place and humans smarter and more efficient can be attributed to science in one way or another. Science translates into important thinking, problem solving, and analytical skills that we need to learn as early in our lives as possible.
Maybe I'm just a nerd, but I liked doing science fairs when I was in Elementary school. Treasure those moments, because they don't last long! Just wait till you get to high school, there are a lot more stressful things then science fair projects.