And some people don't have an inner monologue. It's not specifically mentioned in http://slatestarcodex.com/2014/03/17/what-universal-human-ex... but it's of that same class of thing; there are certainly hits on Google for people claiming not to have an inner voice, and I didn't even bother reading the article on psychologytoday about it.
I didn't say that all "people" have inner voices (by which I meant inner life). But by that definition, it's a requirement to be conscious.
Let me set the record straight, though. I'm not claiming to not have an inner life; I'm claiming to not have an inner voice, except if I'm reading "out loud" internally or whatnot. (Which is useful when writing, but not necessary.)
I just use other modalities.
To the best of my knowledge there's only one guy, a philosopher, who's claimed to have no inner life at all--and I don't think I believe him.
Consciousness is usually only one of two things; either "being aware" or "the experience of having an inner voice".