Why is it a problem to have imaginary conversations in your head?

I tell this funny joke. You are driving in Austin and you see some crazy person talking to a stop sign, and you think, that person is crazy, they are talking to a stop sign. That is nuts. I am not rolling down my windows. Then you drive off and think, you know what, next time they tell me this, I am going to tell them that, and then I will say this, and then they will say that. We start having imaginary conversations in our own head, and we think, well, I am not like the person at the stop sign. Bro, you are the same person. You are as crazy as they are.