Humans are social beings. We depend on each other; not everything we need to do can be done by ourselves. We do not produce every food we eat every day, and the same applies to practically every other aspects of our lives.
We often hear flat-Earthers ask if we have researched by ourselves all the things we claim. If we have not researched it by ourselves but only rely on information from third-party, then —according to them— we should not accept the information. It is merely their way to undermine society, and disconnect us from the rest of society.