Princess Smiley and princess Nikki love to humiliate. They are the kind of people who like to humiliate a guy before sleeping with him. They like to dominate and then make a guy do what they want. That is why they used their boots to dominate this guy, make him feel a little pain and then they fucked him after that as they were turned on with how he handled it all.
Mistress Kimi and her friend mistress Domi were not impressed with the behavior of this loser and they had to make sure he learned his lesson the hard way. And that is why the mistresses chose to use their boots to torture as well as to dominate him. He was in a lot of pain and he had to endure a lot of humiliation as he was made to lick the boots.