To be honest...to tell you the truth?

Ever notice that some phrases make you stop and wonder about what the person is really saying? How many times have you heard an interview with a politician (Ha), sports star or expert who says something like "to tell you the truth" What does that mean? Were the first 10 minutes not the truth? Same thing for people who, in a discussion, will say "to be honest or if the truth be told..." I dont know why but I starting thinking about these phrases the other day. I was watching an interview with a professional basketball player at the time he said one of these phrases. It stuck in the useless interest part of my mind. Makes you wonder why people say these. We all do it. These phrases all beg the question about the real truth of the conversation. It is almost as if the person has only said things untrue to that point. I couldnt resist thinking that if we say these things what does it say about
what we really mean?