Because what these mistresses wanted was to have a good time, they thought that these guys would give it to them. But the guys turned out to have small dicks and these mistresses could not fuck them. So they had to come up with a different way to have fun at their expense and the best one for them was to turn them into foot slave as they made fun of their small dicks.
Mistress Sofi was not please to find out that her slave liked to take shortcuts and so she had to punish him so that he stopped that habit. The mistress made sure that he learned his lesson and learned it the hard way. That is why she chose to trample him with her bare feet after making sure they were smelly. He never wanted that humiliation again so he complied with her orders and instructions.
Mistress Kira and her friend mistress Sofi noticed that this guy had a crush on them. He was always looking to hang out with them and do things with them. The mistresses laughed at him as he did not know what he had gotten himself into. They had him lick their feet and do other humiliating things for their fun. He regretted his interest in them as it was not what he thought it would get him.