True. If FE is to have the slightest shred of credibility, you have to postulate a vast world-wide conspiracy anyways, which is already extremely improbable. But I like to think of the FE vs. RE debate here as a game (which it essentially is, since more-or-less-nobody actually believes that the Earth is flat, although many here have adopted that pose). The goal of this game, for the round-Earthers, is to prove, using only experiments they have personally conducted or observations that they have personally made, that the FE model is impossible. The goal of the game for the flat-Earthers, is to produce a model convincing enough that the round-Earthers can't reach their goal, and to expose the logical fallacies and errors of math, physics, and so on in the arguments of the round-Earthers. Postulating a huge globe-spanning conspiracy puts the two sides on more equal footing, since it's much harder (but still possible!) to prove that the Earth is round using experiments and observations that you can personally perform.
Of course, the round-Earthers have a huge advantage in this game, but then there are also a great many idiots who adopt the round-Earth position, who make many flawed arguments, so the flat-Earthers have many opportunities to score points.