probably less of a reflection of the animal and moreso that we've learned how to design toys that really interest the brain.
humans can use juggling sticks as a toy, but I doubt any animal would care since they see sticks all the time. bright colors, noises, interesting shapes and textures, etc.. even though balls might not be too interesting to use, how often do you see perfectly round yet still light objects in nature? the closest would be a round rock, which is too heavy to bounce around. the whole motion of the ball is different from anything the animal would've experienced.
