In many different games, such as Minecraft and TF2, the default texture is a black and purple checkerboard. Even games that don't use that exact texture incorporate elements of it. Borderlands 2 uses a white and purple checkerboard, and Skyrim uses a solid purple texture. Why is the black and purple checkerboard so prevalent as a default texture?
The main goal of a default/fallback type of asset like this to be noticeable. That's why very high intensity colors (pure white, red, purple, or whatnot) are often used. They generally would not normally appear in the scene.
Checkerboard patterns can create moire effects when used as textures, or simply provide extra visual noise (especially when the pixel coverage of the asset is small), helping to increase the visibility.