Alot of what the brain does is process sensory information, other great chunks are devoted to getting us moving, but from time to time we use it to do what we think of when we think of it, ie think.  And when we are thinking we are doing really complex things that only appear simple from the outside, so making associations, sequencing & prediction are all required to grasp Cause & Effect. While a repetitive task is the very essence of boredom to most adults it is worth remembering the joy in one's own ability that it causes in the young.