I used to have an internal monologue when I was a kid, but it felt less efficient, so I trained myself out of it by around 20. By most objective measures it did make my thinking more efficient but reduced my wit and articulation.
I do imagine conversations with people though, usually when I'm trying to work out how to say something. When I figure it out, I stop the imaginary conversation. Occasionally these imaginary conversations become so vivid that I'll actually speak out loud. It's a quirk of mine that my friends and family giggle about. In my defense, Adam Smith did this too, so I'm in good company.
I do imagine conversations with people though, usually when I'm trying to work out how to say something. When I figure it out, I stop the imaginary conversation. Occasionally these imaginary conversations become so vivid that I'll actually speak out loud. It's a quirk of mine that my friends and family giggle about. In my defense, Adam Smith did this too, so I'm in good company.