Because you couldn't pass a Turing test, even for practical purposes with that approach. Passing the Turing test is a problem that cannot be solved by big data alone. You have to model not just language patterns and word sequences but the prior causes for those word sequences. The prior causes for the words (and images, and videos in the original example) are ultimately desires and experiences of real human beings and truths about the universe.
In other words, a computer has to actually model the world and the changes to the state of the world as the conversation goes on in order to pass a Turing test. I didn't read anything in the original description to suggest that was happening.
In other words, a computer has to actually model the world and the changes to the state of the world as the conversation goes on in order to pass a Turing test. I didn't read anything in the original description to suggest that was happening.