[jimmaswell]

In text adventures there was a limited grammar that the parser understood that was English-like, which you had to express your actions in: get lamp, put lamp on table, eat fish, look sword. This is easier than if the parser tried to let you use fancy English sentences that it'd probably get wrong often and that you would make more mistakes in because the line is blurred between what you're allowed to say or not. That would be a point between the simplistic text adventure grammar and perfect natural language parsing, with the simpler grammar being preferable. I can see the same being true for voice commands.

[lsaferite]

As a side note, it might be funny to hook one of these voice command systems up to a z-machine VM. The command set is very limited as you pointed out, so it should easily be able to handle the input side. And the voices, while still robotic, seem pretty good as well. With games like Zork being fully text based you could easily turn it into a conversational game.