why does/ doesn't phase count when you analyze a voice signal?
Phase will have an effect on the mathematical analysis of speech signals however the traditional practice of speech (audio) processing has evolved based on the observation that human listeners do not have a phase sensitive hearing mechanism, which indicates (supported by experiments) that phase may be neglected in most speech processing applications, at least when compared to the frequency magnitudes. You may search the site for other related answers. But I think the most extensive source will be the audio engineering society.