A cat biting its owner's hand could be a habit, a bad habit formed when it wasn't corrected or trained as a kitten. It could also be due to boredom; most cats nowadays are kept indoors and rarely go outside. Lacking playmates, the cat may naturally treat its owner's fingers as toys.
Some cats might be biting because they see their owner's hand as prey. Cats are very curious animals and are naturally interested in moving objects. When a cat sees its owner's hand moving around, it might mistake the owner's finger for prey and lunge to bite. Owners should correct this behavior promptly to prevent it from developing into a bad habit of biting people indiscriminately.
