There are many reasons why cats like to squat in the shade. One possible reason is that cats find it more comfortable this way. Shadows are generally less intense than light, so they are cooler in the shadows. Cats may also like to rest in the shade, where they are protected from direct sunlight and heat.
Another possible reason is that cats may feel safer in the shadows. Shadows provide a secluded place where cats can observe their surroundings without being discovered. This is one of the reasons why cats like to crouch in certain places waiting to be hunted. Overall, cats prefer to squat in the shade probably because they are more comfortable and safe. However, every cat is unique, so this preference may also vary from individual to individual.