More than 3 people talk to Cortana, in fact more than 3 just in my office. Admittedly this is just whilst building laptops via Autopilot, and the comment every time is "shut up you harridan" or something rather less polite.
I don't get the obsession with these voice assistants though, I was given an Echo Dot and really only use it as a timer in the kitchen or sometimes for music, and the dozy bint always suggests music I'd have to pay for, rather than have already bought, so spends most of her time switched off.