1/ If human brains would have worked same way and everyone had same perspective of looking at things, then it would have been much easier to build an AI conversational system.
2/ Everyone would have interacted with the system the same way and hence there would not be any possibility of the conversation going in wrong direction.
3/ So its difficult to build such systems that can take same input in different possible ways as compared to any other systems which take the input in standard format.
4/ Conversational Systems are here to stay but may take time to become part of our daily lives.