Much like human children, baby animals are full of energy and enthusiasm. This gives them the drive and stamina to learn the co-ordination and survival skills that will keep them alive.
During these early days, a strong bond between mother and offspring is vital. The young goat will absorb invaluable skills from watching its mother and interacting with her, which is probably why the weary mother goat tolerates this horseplay for such an admirable amount of time.
Eventually, mom has enough and wanders off, but her little one is close behind, ready for the next adventure.