From a technical aspect, they don't need to. But that's what people expect. John Q Public wants what he wants regardless of what the techies think he wants.
I've never understood the fascination with voice control. It's clumsy, it's inaccurate, and honestly it's a bit embarrassing to use alone or in public. Yet, "everyone" seems to want it, despite the fact that spatial-sensor-based (e.g. motion sensors, Kinect, etc. -- note that I'm not talking about gestures, which have the same problems with ambiguity as voice) and tactile controls are much more efficient.
Reading this made me picture trying to drive a car by voice: "Turn left. Left. Further left. More! AHH! NOT SO MUCH!" Here voice control seems like a desire to avoid having to clearly specify your request. "Didn't the car KNOW where I wanted to go? Doesn't this spreadsheet KNOW what numbers I want? Doesn't this fast food menu KNOW what food I want? Maybe if I could just tell it..." I suspect that voice recognition will be popular in the future, but it will seem a lot less sexy if users are still required to clearly specify what they want.
You've got it exactly -- the more important thing, IMO, is systems "knowing" what you want, predicting your behavior, in a way that is completely effortless, transparent, and expected. I'm doing that now with my startup, using pre-scripted actions, but hope to see user-adaptive, learning systems (e.g. the Nest thermostat) find their way into everything.
Not so sure, people are used to buying allot of things without needing to use their voices.
When amazon launched I doubt that the fact people couldn't specify which books they wanted to buy via voice control was a major hurdle.
I think the next generation will view buying most things via some text or graphics based menu as nothing unusual at all.
You don't walk into book stores to ask employees for the book you want. You browse, look, read, and finally select a book. No interaction with humans required. (There's human interaction at the point-of-sale, but you still don't have to speak to checkout.) Of course, if they didn't have the book you wanted, you might have to speak to a human to get it ordered ... if they didn't have computer kiosks for you to use instead.
Moving this type of sale onto the internet was not a change. Moving the food service industry, where human interaction is expected, into an environment without human interaction goes against people's expectations and habits. Is such a change technically feasible? Yes. Is it practical? Yes. Profitable? Sure, if you can change people's expectations.
I'm not saying it's a bad idea. I don't even think it'll be a difficult change. I personally would prefer it. But the first chain of restaurants to offer automated food service (and I do believe it'll need to be a chain) has many psychological barriers to overcome, in its investors and its customers.
