I more discounted them because they don't have a collective society. They may be sapient, but they don't have a collective leadership structure (that we know of), oral (telepathic) history traditions, shared religion/worldview/myths, forms of music or dance, medicine, or anything that resembles an actual society (not counting buildings and agriculture, because even among humans that's an incredibly reductive and colonialist way of defining a society).

Dragons may be sapient, but they aren't "a (society of) people" in the same way that humans, elves, dwarves, urgals, and werecats are "peoples".