Actually, there's a really good reason for this.
In the northern hemisphere it's clearly obvious that the stars are centered above the north pole, if you observe them for a couple hours, they all appear to rotate around a single star... Polaris, the North Star. People have been using Polaris to navigate at night for ... well forever.
Flat Earth nutters have historically come from the northern hemisphere, and as such are well familiar with the north star... hell, everyone is. Everyone went camping and looked at the stars at least ONCE in their life. These guys are also religions nuts, and believe that scripture says the world is flat... So, combine two beliefs that the person has:
1) Stars rotate around a center, which is over the north pole.
2) Scripture is the inerrant word of god, and says the world is flat.
And viola! North pole centric flat earth map. The big two in this field are Samuel Rowbotham (up to about 1880) and Charles Johnson (Up to about 2000) Both were major religious nuts who lived on the northern hemisphere.
Of course, the stars appear to rotate around the south pole as well, which disproves the hypothesis... But Rowbotham, Johnson, et al didn't know that as they've never beeen there.