Most girls are insecure and are typically envious of their friends clothes, boyfriends, physical attributes, etcc... Ashley and Sam are no exception, especially since they both have great asses are both EXTREMELY ENVIOUS of each other's well formed derriers. That is why they can't seem to keep their hands and lips off each other's asses but at the same time yanking on those panties to cause a little pain, that need to cause each other some physical pain stems directly from the mutual envy they have, at least these two friends have found a playful way of letting it out so to speak.