We can't avoid applying human paradigms to animal behaviour. Cats strike us as introverted and cynical so they serve well the purpose of criticizing humanity; by playing the role of a cat, people can disclose about the pointlessness of life without sounding too bitter or too philosophical (much like dogs facilitate talking about how humans can be loyal, friendly and honorable).
Nonetheless, opinions about dogs and cats really are homogeneous. Maybe this means our ideas about those animals have been constructed over time. We wouldn't be so eager to call an eagle "loyal" or "smart". Our relationship with dogs and cats is so long that we've had enough time to carefully craft their images.