I think it's partially region-based, in the United Kingdom, Siri is a male. (Perhaps it's somehow related to butlers, where as in the United States, secretaries

I think it's partially region-based, in the United Kingdom, Siri is a male. (Perhaps it's somehow related to butlers, where as in the United States, secretaries were more common.) Betty was also likely named Betty because of the last three letters, there's no voice with the application, it's only gendered because of the name.