Cats eat grass to aid digestion. Sometimes they are sick, sometimes it passes right through them and sometimes it gets stuck in the throat and when they sneeze it comes back down the nasal passage, as happened in our boarding cattery once (entailing urgent out of hours expensive trip to the vet).
A kitten looks endearingly at a human, who falls for its charms. The human takes it home, provides a comfy warm bed, feeds it on demand, lets it out of the house on demand and lets it back in on demand. The cat arranges things so that all it has to do all day is relax, eat and sleep. And the cat is the stupid one?
Don't think so, jezzatt