A dysfunction in sensory integration can cause a person to have problems processing sensory information, which can present itself in a preference for unusual colors and repetitive behavior such as flapping hands for self-stimulation.
It hugs the body with a snug fit which helps prevent chafing that can result when wearing loose fitting shorts that get damp from sweat and then rub and irritate the skin when repetitive movements such as cycling are performed.
Others are compulsive eaters who, as the result of a chemical imbalance in the brain, engage in eating as a repetitive, obsessive behaviour, in much the same way that some obsessive-compulsives wash their hands repeatedly.
Rhythmic and repetitive motion comes naturally to moms and dads, and it's evident anywhere you go as you witness daddy's bouncing their babies on their knees and moms swaying back and forth with babies on their shoulders.
The best Christmas gifts are personal, of course, but if you're crafting for a whole bunch of people you can alter the colors or design for each piece while still using a somewhat repetitive pattern that saves you time.