Adding "mirrored" courses is a simple and easy way to include more content within a game.
By using assets already in the game, a mirrored map takes up very minimal space on a game medium. This technique is especially useful for large sized maps or if developers are working with limited storage space, such as a cartridge.
Because a map has to be completed and tested before it is mirrored, it makes a mirrored map easy to debug.
In an extreme case, The Legend Of Zelda: Twilight Princess for the Wii was completely inverted horizontally, including Link's character model. This was made so that Link could be right-handed, generally matching the actions of mostly right-handed gamers. As an offset, the sun in the game rises and sets in reverse direction, characters shake hands using left hands, and obviously Link is right-handed despite being traditionally left-handed throughout the series.