All of these measures are imperfect, but they are indicative and, unless they contradict each other, they could contain valuable information for policy purposes. Although there are strong arguments for taking note of market signals, this does not solve all our problems. No matter how well-informed markets are, or central bankers for that matter, they do not have perfect foresight.
As we know, the future is inherently unpredictable. Even if we make policy optimally on the basis of all available information, new information becomes available all the time. Behavioural relationships by their very nature are very difficult to predict.