Flat Earthers believe the Earth is flat because deep down in their hearts they want it to be true and they don't want to accept that they are tiny unimportant beings in an enourmous universe.
"they are tiny unimportant beings" <--- this is a religious belief we learned as children, just like the belief that we are important. Neither is proven or has much real evidence.
As long as we don't see evidence that we have a greater importance within this universe I think it's safe to assume that we don't. We are like insects in a forest.