I always though the drives worked, more or less, willingly with the people. Though some are mistreated. If they are cognisant enough to need therapists for mental health due to mistreatment, then having voices would really be quite natural, so as to ensure they can fully make their wishes known. Though I also tend to view the Nae'hyn, not only as the builders of these drives, but also as espers who tend to have a psychic link to these AI's. Or, perhaps, thanks to B'Nari technologies, each implanted with cybernetics to be able to "be the voice" as it were for these specialized ship engines. If they do not have voices themselves. As well as attempting to be their protectors against those that would mistreat them. Unless, of course, the Nae'hyn aboard is killed, or worse.

Just my honest opinion, though, to be candid.