"Yes, but we can circumnavigate the South easily enough," is often said by those who don't know, The British Ship Challenger recently completed the circuit of the Southern region - indirectly, to be sure - but she was three years about it, and traversed nearly 69,000 miles - a stretch long enough to have taken her six times round on the globular hypothesis. This is a proof that Earth is not a globe.
The most commonly accepted explanation of this is that the space agencies of the world are involved in a conspiracy faking space travel and exploration. This likely began during the Cold War's 'Space Race', in which the USSR and USA were obsessed with beating each other into space to the point that each faked their accomplishments in an attempt to keep pace with the other's supposed achievements. Since the end of the Cold War, however, the conspiracy is most likely motivated by greed rather than political gains, and using only some of their funding to continue to fake space travel saves a lot of money to embezzle for themselves.