There are several reasons that people might believe that the Earth is flat:

1. Some ancient cultures believed in a flat Earth, such as the Greeks and Egyptians.
2. The Bible mentions a flat Earth in some passages (e.g. Isaiah 11:12 and Revelation 7:1).
3. Some people think that the horizon always appears flat, regardless of the observer’s location.
4. It is easier to explain certain phenomena, such as eclipses, on a flat Earth model.
5. Some people think that a round Earth would be unstable and would eventually collapse in on itself.