Earlier quoted context omitted.
I feel the same way about having somebody constantly chatting in my head :) I'd assume for both of us it's mostly fear of the unknown.
How would you think through complex scenarios otherwise? Like: "How does the current US president influence global welfare?" (relevant, but rather trite, I know). Genuinely curious how you could form an opinion or at least analyze the question without verbalizing the ensuing self-conversation in your mind. Much (abstract) thought is informed by language.
It's hard to see how this works with such a complex question though. By its nature it's actually impossible to put into words. It's my theory that we all think like this, because it's literally impossible to think "in language", but some people need to have it as some type of security blanket and some don't.
Every time someone says they have some inner monologue I can ask where this comes from. Your inner monologue also needs a source and that can't be language again. You cannot source all thought you have about this question just from those words alone. Your mind is making all types of connections that might eventually be convertable into words, but are themselves absolutely not verbal.