Why are the "wants and passions" of the Houyhnhnms less than those of humans?

this movie depicts a society where lying doesn’t exist, until in a strange turn of events, the protagonist is able to lie, which results in a complete change in their societal structure, from media and advertising, to personal relationships (both romantic and social). It’s quite comical seeing the protagonist, Mark Bellison, interact with his former coworkers, peers, neighbors, and even complete strangers once he realizes he possesses the power to lie. We see a similar parallel with Gulliver and the people of Houyhnhnms; he sees them almost as children because of their incapacity to see the maladies that are in the world. Gulliver even goes forth to saying that “their language doth not abound in variety of words, because their wants and passions are fewer than among us