Bicameralism seemed a lot sillier to me before I found out I had aphantasia (lack of a mind's eye), and most people see imaginary images while awake. Hearing the voices of imaginary gods doesn't seem all the different from seeing false images.
There's a gap in the language and between minds that makes it near impossible to understand and communicate about the actual experience of thought. There seem to be a lot of people mistaking these gaps for the presence of some unique disorder and calling it "aphantasia".
As far as I'm aware, most people don't see vivid imagery while awake. I can certainly imagine something but it is not a vivid image like reality, my mind's eye is ghostly and dreamlike.