"How are you?" is a nice question. It's a friendly way that people in the USA greet each other. But "How are you" is also a very unusual question. It's a question that often doesn't need an answer. The person who asks "How are you?" hopes to hear the answer " Fine", even if the person's friend isn't fine. The reason is that "How are you?" isn't really a question and "Fine" isn't really an answer. They are simply other ways of saying "Hello" or "Hi". Sometimes, people also don't say exactly what they mean. For example, when someone asks "Do you agree?" the other person might think, "No, I disagree. I think you're wrong..." But it isn't very polite to disagree so strongly, so the other person might say "I'm not sure." It's a nicer way to say that you don't agree with someone. People also don't say exactly what they are thinking when they finish talking with other people. For example, may talks over the phone finish when one person says "I've to go now." Often, the person who wants to hang up gives an excuse "Someone's at the door." "Something is burning on the stove." The excuses might be real, or not. _ The excuse is more polite, and it doesn't hurt the other person. Whether they are greeting each other, talking about an idea, or finishing a talk, people don't say exactly that they are thinking. It's an important way that people try to be nice to each other, and it's part of the rule of the game of language. When a person disagree with someone, it is polite to say "  _  ".
You are wrong. I disagree I'm not sure I'm sure I disagree No, I disagree