This is not in the debate section so I can't explain the real reason. But you have to realize that all these flat earth theories are made up to fit conditions IF the earth was flat.
Allow me to tell you a story. In the 1800s, no one used nuclear reactions to explain where all the energy the sun produces comes from. How could they? Instead, they presumed that the energy came from the gravitational collapse of the sun itself. They had models for that. And they could use them to estimate the sun's age. I won't repeat the whole derivation for you here (though I can, I have it in a notebook somewhere), but they came up, using what appeared to be very sound methods and correct mathematics, with an age of about 32 million years for the sun.
Now, this was understandably a controversy because there were those who claimed the earth was older than that. But it was nonetheless the "accepted" number because of the made up condition they placed on the sun (that its energy comes from its own internal pressure due to gravity).
Today, they have come up with the idea of nuclear reactions, and have used that condition to arrive at an age of about 4-5 billion years for the sun. Welp, this is sure older than the earth, so we call it golden, but the only thing that's changed is that someone made another condition fit the situation. No one's been there. We can't directly measure hydrogen fusion in the sun's core, only the energy it allegedly produces.
In recent centuries, physicists made up a thing called aether to explain how light propagated through a vacuum. Today, they've made up a thing called dark matter to account for calculations for masses and the rotation of clusters and galaxies showing far more mass than observed. "Accepted" science is full of examples of a condition being invented and forced to match observations.
We say the earth is flat because the earth appears to be flat. Yet when we discuss the nature of the cosmos starting from this assumption, we're making things up and forcing them to fit our model, and that somehow lacks credibility?
Hello pot, this is kettle.