How many times have you been a conversation, or been listening to one and heard the words "let me finish!!" usually in an excited tone.
Its seems us humans have a very strong tendency to interrupt people when they are talking. This obviously annoys/angers people, and sparks them to chime out the aforementioned words.
Cats on the other hand, do not have this problem. I just conducted an experiment with my occasionally noisy cat Ruby. She gets into winy moods where she mixes up her speech with a variety of murmurs, mechs, and meows. My experiment reveals if i wait for her to finish what she's saying, then launch into conversation with her (maintaining eye contact), no matter how long i go for (within reason, up to 20 seconds or so) she won't interrupt me and will stay attentive and focused on me. Only when i complete my speech will she then, normally within a few seconds, respond with some of her usual noises. I think she's agreeing with me.
In some ways cats are far more polite than humans.