What's the benefit of telling people that the earth is flat? What needs to happen for you to see that the earth is a sphere.  Who's they? I've done research (not physics research) and there is no motivation to lie to people. Remember that the people doing the research are usually normal people who passed a lot of classes. A lot of thing would not make any sense under the flat earth model. Satellites would not work, the seasons, night and day... etc.