The responses are based on the accumulated knowledge of humans and not machines. The systems have not thought through anything and understand nothing. A process of analysing or pattern matching the input question with the data stored retrieves an answer. But that data stored is human knowledge and human effort not machine.
If you look very carefully at the results obtained, it either contains "interesting errors" (for which an intelligent human would pick up) or it is a summation of human knowledge.
The answers still have to be tested and confirmed for rationality and applicability by humans. In other words, this is a tool like all tools created by humans.
I have seen too many examples of what are supposed to be correct answers that contained subtle and not so subtle errors.
Like every system we have ever made, Garbage in gets us Garbage out. We are the ones responsible to checking those answers and making sure that they make sense in the real world.