People talk to each other all the time in airplanes too, and even libraries, but it turns out that people are both more understanding of people talking to other humans currently present (rather than say on a cell phone) and people are better at talking to other humans currently present respectfully than they are at talking to devices (or at least people via devices, but I think we can extrapolate).

I agree if it was already the social norm it wouldn't be a problem (same with Google glass), but it turns out that the technology being ready isn't always enough to make the social norms change.