Comment by vidarh

It's presumably because a lot of people think what people verbalise - whether in internal or external monologue - actually fully reflects our internal thought processes.

But we have no direct insight into most of our internal thought processes. And we have direct experimental data showing our brain will readily make up bullshit about our internal thought processes (split brain experiments, where one brain half is asked to justify a decision made that it didn't make; it will readily make claims about why it made the decision it didn't make)