Some countries decided to partition their territories into a rectangular or square grid. But the Earth is spherical, and it is not possible to divide a spherical surface into a perfect rectangular grid while maintaining the perfect angles, distances, and areas.
To solve this problem, land surveyors implemented grid corrections. Every certain distance, parts of the grid are shifted away from each other. Therefore, an equal area in each division is maintained as much as possible by giving up an entirely lined up grid.
If the Earth is flat, it is not necessary to have this compromise. It would be possible to divide the land into a perfect square grid system.