Back when I was in sales, mostly on the phone, I read loads on the subject and all the advice (particularly women specific) was to drop your voice a few semi tones and speak more slowly. This apparently gives of an authoritative vibe or some shit.
I then took up smoking (not to get more sales!), and my voice has 'naturally' got deeper. I definitely still use my lower voice in certain situations with men. In my mind, particularly during even mild conflict, the natural inclination to speak faster and higher pitched turns people off, leaning more towards the sexist 'shrill' and 'hysterical' terms rather than people taking you seriously. I do think there's something in it, rightly or wrongly.
I had to look up vocal fry as I only know it as a singing technique. I heard some examples and it mostly sounds like that stereotypical middle America teen/early 20s, Paris Hilton type wannabe. I can see why it would mean you're not taken seriously!