During early childhood, I was raised being taught many things such as: Christianity (+existence of other religions), Creationism, Evolution, Astrology, Astronomy, that Santa brings presents to your christmas tree via flying raindeer and entry through a chimney (which my house didn't have at the time, so I was immediately skeptical on this detail). As may be known by the reader, some of these things contradict one another, and can have a certain effect on a growing individual. With a stance of skepticism from early on, I questioned all of these things: How is christianity any more true than Judaism or Islam? How did god create humans only a few days after the rest of the earth, when dinosaurs have been around millions of years before humans? How can the positions of stars in the sky at your birth determine your fate? Why can't I see nebulae with my bare eyes? Has anyone really seen a black hole? Why is the sky blue, when prisms split light into all colours? Why do ALL of my presents seem to come from my relatives several days before Christmas? As Evolution, and Round-Earth Astronomy produce models consistent with my experiences in everyday life, I logically deduce that they are closer to the truth than anything else. Any alternative models will be rejected until they explain all and more than the ones currently accepted.
As you can see, my belief in a round earth is not the result of a blind following of what I read in the textbooks and hear from teachers, but the result of years of objective analysis of all theories presented to me. So far all attempted explanations I have encountered here are mathematically unsound or unresolved, are questions regarding my inefficient use of language, or are confusing lines of wordplay which make no impression on my mental image of the universe whatsoever.
This is why I have yet to believe in the Flat Earth Theory.