[Dueller]

"[I was arrested for public drunkeness]...I had the right to remain silent but not the ability." --Ron White

The OP asked the basic question Why would anyone incriminate themselves. It was in the context of a suspected DUI stop so this discussion has degenerated into a debate over implied consent law.

As to core original question people let's change the facts a bit. Suppose you are pulled over because your car was observed a a murder crime scene. The officer approaches and in the course of a brief investigatory stop asks you are there any weapons in the car. You have a CCP AND THERE IS A PISTOL IN YOUR CAR. WHAT IS your answer? What if he then asks do you know anything about murder of John Doe? Do you say we'll I only shot him twice in the leg but I'm no murderer much like a "I've only had two beers" response to have you bee drinking question.