Why are slave men so often depicted eating from a bowl on the floor?
If a male slave is completely humble and obedient he may be lucky to be treated by his Domme Owner like a pet. When not performing chores that require him to stand the slave lives on hands and feet, crawling on all fours like any other pet.
If a slave man resists his enslavement, dares to be impertinent, performs tasks lazily or carelessly he must be constantly humiliated. Humiliation is always likely to include being treated like a beast. Forcing him to feed from the floor is a forcible technique to remind him of his inferior status.