Haven't people been talking to phones in public since the StarTac? Siri's big selling point is that you talk to it in the same cadence as you would a human on the other end.

Actually I don't think people have been talking to their phones (voice command) as much even though the feature has been available for the longest time. One reason could be that the feature was very poorly implemented. What these features lack is the context that we so readily assume when talking to a person.

The reason at least I don't use voice commands is because I feel stupid doing it if the phone does not understand me in the first attempt. I haven't used Siri myself. I use windows phone and it has damn good voice menu system. But I still don't feel comfortable enough to use it.