Because dogs interpret situations differently from people and have different social codes of conduct, misunderstanding that causes dogs as a whole tons of problems. A dog that understands his/her place in the pack structure is much happier than one that doesn't, and will tend to have less behavorial problems which for many people could cause them to give up the dog.
Dogs are different from humans in their need for affection. A submissive dog that is below the alpha in the pack licks the alpha dogs face (petting) and lets the alpha dog initiate interactions.
actually because of the described actions I would lean more towards a viewing them as a threat. When stalking prey canines don't act like the above description.
as someone else mentioned it has to do with pack dynamics. Generally speaking most dogs do not require measures like this, but there are times when things that seem silly (such as allowing a dog on a bed, or couch, etc) are needed to establish pack heirarchy.