Many people treat kids like inferior beings, using "cute" voice, not giving them a chance to say their word, make a decision and such. Do you think such behavior might bring harm to the development of their personality, and they should be instead treated like adults, but just less experienced, so with understanding and patience?
I remember my father giving advice to my brother not to talk to his child in a childish voice. I agree with treat them like an adult but with limitation. It is also good to be playful sometimes.