The why question is easily answered if you see how many negative reactions their choice of voice caused. A gender-neutral voice would have just avoided annoying a certain percentage of the population, including me.
I'm happy if advertising stops hitting the sexy/cliched stereotypes.
Sometimes the Guardian goes a bit far but OpenAI could have avoided this kind of article: https://www.theguardian.com/commentisfree/article/2024/may/1...
(Edit: I guess I was being slightly inflammatory with my first sentence. I think the default voice should be gender-neutral and then let the user choose what makes them happy. I don't think it was clever of OpenAI to use a sexy female as the default voice in their demos as evidenced by us having this discussion)
For whatever historical reason, the majority of Indo-European languages assign genders to nouns, so apparently it does make some sense.
Also, I'm offended on behalf of all Cylons.