Part of that is down to the fact the person that takes your order also helps clean when not busy, smiles at your kid, ejects unruly customers and upsells to supersize more persuasively than a flashing red box (which was a large part of my original point)
But part of that is also down to the fact that the average person is really bad at using a human-machine interface (and that ain't gonna be improved in a busy commercial environment by voice-recognition technology any time soon)
I mean, I see a lot more automated kiosks in supermarkets than I used to. Usually I use them in preference to human kiosks. Many other people have precisely the opposite preference, and they have money to spend too. Overall, the kiosks increase the throughput of the store, but that's because there are more of them due to their smaller footprint than the checkout counters they replace. In the hands of the average person trying to use the system they're certainly not more efficient than a competent checkout operative, and require a human for every few machines to deal with their idiosyncrasies and frequent failings, and manage the queue.
And the automats, which are a far better human/machine interface than some talking touch screen connected to the kitchen because you literally see the freshly-made fast food, put money in the slot and open to receive it? They've been around for a century now, long before Ray Kroc and Colonel Sanders got into the industry, and they've repeatedly failed.