Flat Earthers hold their belief because they know something's off about the official narrative and it's the closest they've gotten to the truth. It's the most stigmatized and ridiculed theory, not because they believe in a flat earth, but rather the other truths many have uncovered along the way.
(media.communities.win)
Speculation
Most people that claim to be flat earthers are just parroting shit they've seen and haven't given it any thought.
Most critical thinkers that have taken the time to research flat earth and globe theory, see the faulty arguments of both theories, and thus remain skeptical. If you doubt the globe model, or even lean towards it but wish to see proper science, you're labeled a flat earther.