Let's be honest

Have you ever thought about the term that people often use....let's be honest? 

I mean, let's be honest, I use it (point and case). But I was thinking about it today and in doing so it made me come to realize just how strange that phrase is. We don't ever say, "I'm going to lie to you." or "Let's NOT be honest." So why is it that we feel the need to tell people when we're being honest? Has our society gotten so bad that you actually have to publicly announce that you are an honest person, or the exact moment that you are being honest? And does that mean that if you don't start your sentence out with this you're just not telling the truth the entire time?

Alright, alright, I know this is very random and I'm being pretty silly about it, but it was one of those phrases that was fun to think about and wonder how it came about and why people use it.

Let's be honest, you are curious now aren't you?