Dragon's are at the bottom of the food chain. The ones that get yelled at, taken from, abused and treated badly. Welsknight knows this. He also knows his place. So in order for him to be treated as an equal, he pretends to be a regular boy. However, Impulse finds out about his secret and Since the knight knows how he'll be treated by the hermits and the way X will react, he does whatever he can to keep his secret.