Because it is based on myths and urban legends, instead of science or facts.
Dude, do you even know where the Flat Earth hypothesis comes from? It comes from the freaking bible! A book about 5000 years old with people that can walk on water, and divide the ocean into two and fire comes from the sky and burns cities simply because there were some homosexuals in them. Now, if you call that science and facts, then yes, the planet is flat.
I wonder, why hasn't fire burned down NYC? The number of homosexuals here is increasing dramatically.
I'm not a bible scholar but I am curious. Can you point out passages that claim the earth is flat?
Let me see if I can remember.
Here are some:
1 Chronicles 16:30: “He has fixed the earth firm, immovable.”
Psalm 93:1: “Thou hast fixed the earth immovable and firm ...”
Psalm 96:10: “He has fixed the earth firm, immovable ...”
Psalm 104:5: “Thou didst fix the earth on its foundation so that it never can be shaken.”
Isaiah 45:18: “...who made the earth and fashioned it, and himself fixed it fast...”
And more:
Daniel 4:10-11: "the king saw a tree of great height at the centre of the earth...reaching with its top to the sky and visible to the earth's farthest bounds.”
Matthew 4:8: "Once again, the devil took him to a very high mountain, and showed him all the kingdoms of the world in their glory.”
If the tree can be seen from anywhere in the planet, then the planet must be flat. For in a round planet, the tree wouldn't be able to be seen due to the curvature of the Earth.
Same for the so-called Jesus. He was able to see all the kingdoms from a mountain, so, the planet must be flat.
I am not saying that these are proof of the flat Earth, (I'm a RE and an Atheist) but I showing you that the hypothesis of FE comes from ancient times (when the bible was everything).