Dogs may sit on their owners' feet because they find it an intimate way to interact with their owners. Dogs like to bond with their owners, so sitting on their owners' feet may be a way for them to "claim themselves to themselves." In addition, the dog may sit on the owner's feet to protect the owner. Dogs instinctively believe that they need to protect their family and home, so sitting on their owner's feet may be a natural display of protective behavior for dogs.
Finally, dogs sitting on their owners' feet may also be because they like to stay in contact with their owners. Dogs are social animals and they enjoy spending time with other animals and humans. Therefore, sitting on the owner's feet may be one of the bonding behaviors displayed by the dog. Overall, dogs may sit on their owners' feet for reasons of intimacy, protection, and socialization.