I'm wandering:
If earth would be flat, it would be much easier to create an accurate map, as there would no projection needed, just "scaling".
A 2D world could easily be represented on a 2D chart.
Why should cartographers - since centuries - bother to apply complicated map projections and present us charts, that are not as accurate as these could be, but suffer from significant distortions (at large map scales).
... unless earth is not flat.
For over 300 years California was depicted in maps as an island off of the coast of the United States.
How can you appeal to the centuries-long authority of cartographers?
"Around the year 1500 California made its appearance as a fictional island, blessed with an abundance of gold and populated by black, Amazon-like women, whose trained griffins dined on surplus males,"
Yes, folks sure knew a lot about California back in the day.
That aside, consider this: They clearly didn't know the exact configuration of the area,
but they still knew how to find it. That alone contributed infinitely more to cartography than FET has, considering FET has (by your own admission) contributed absolutely nothing to the mapping of the world.
Let's get back to the topic at hand, though: The question you haven't answered. It would be objectively easier to create a map of a flat world when compared to projecting a globe onto a 2d surface. Why, then, have cartographers always made it so difficult for themselves?