Well the GP might not live in the US. I don't, and I have never seen anybody use one of those and I don't know anybody who does either, and I haven't seen them in series or movies either (except sci-fi AI movies). For all I know, an Alexa is just a device to order toilet paper from Amazon when it's out or maybe use it to turn on and off the light in the room if you're too lazy to do it yourself.

Is the demographic that uses these preferentially si-valley people or is it widely spread in the US?

BTW I'm not particularly against home AI assistants myself. But I'm fairly against streaming my audio to a third party that can transcribe and give everything to any snooping fourth party though :) I did read about Google doing this with their assistant's audio, it ended up at contractors doing manual transcribing.