For what it's worth, in my small group of acquaintances, I do hear people now and then saying "OK Google..." and asking questions or giving commands. But I think a lot of that is because I remind the people I'm around, "You have a phone, don't you? Ask it."
Generally speaking, I think there needs to be time for people to get used to the idea that talking to their computers (or phones/devices) actually works fairly well and then more time to transition from old habits (typing) to the new habit (speaking). It may even need the upcoming generation being raised with the AI assistants there before they become truly ubiquitous.
I think the older and wiser generation is distrustful of such technology and the invasiveness of it. I'm generally reluctant to give my devices permission to listen in on me. That said, I've been suppressing the klaxons in the back of my mind as much as I can that Google already knows basically everything about me. I use their browser, I use their email service, I send and receive phone calls and texts/IMs through Hangouts & Google Voice, I use their calendar to schedule events, I use Android which tracks my location, I use Chromecast to watch stuff on TV, I use Google Drive for my spreadsheets and documents. And there's probably even more of my personal information out there in Google's hands that I'm overlooking at the moment. All voluntarily and willingly given to them from me.
With the knowledge that they literally own almost everything a person could know about me, it's hard to keep up what must be a facade of concern about an AI assistant gleaning more information out of me. So I use it in some minor ways.
If I'm at my computer, I'll just "Google" something (using Duck Duck Go). But if I'm out on the go, I'll use a phone (someone else's) to "OK Google..." and ask a question. I also often use voice commands to set up an alarm or timer on my device, or other reminders. When it's as easy as "OK Google... Remind me tomorrow at 3PM to [whatever]" there's no excuse to forget anything again. It can be really convenient.
That said, I have no need or even desire for an AI assistant sitting in my house, always listening and waiting, ready to answer questions or play some music for me. If I need questions answered, I'll ask my computer or phone/tablet. If I want music played, I'll play it on my computer or phone/tablet. Maybe if I had a "smart home" and the AI assistant could preheat the oven for me, or turn on the heater/air conditioner or adjust the lights, or whatever, I might make more use of it. But a lot of those are actually things that I would want to be able to do while I'm away from home. So I'm still not sure I'd benefit from a stationary AI Assistant on the bookshelf of my home.