Cops without their headlights on draw more attention

In the last couple of weeks, I've seen two St. Louis Metro police cars driving around Soulard at night without their headlights on. I have to ask why.
The other night I flashed my headlights on and off, and received a friendly wave from the police officer for my gesture. But when I got home I wondered why the headlights were off to begin with. Did he simply forget to turn them on, or did the drivers of both squad cars have tactical reasons for killing their headlights? Remember, we're not talking about the blue and red row of lights on top of the vehicle. We're talking about basic headlights.
Following the officer's wave, he turned onto an adjacent street with his headlights still off. If he's trying to be stealth, he's going about it the wrong way for two reasons.
First, driving around in the city at night without headlights on is only going to draw attention to you. If you want to drive around in stealth mode, try blending in a little.
The second reason is pretty basic as well - when your headlights are on, oncoming traffic has to look into your headlights. Without the cop car's headlights on, my car's beams were able to nicely frame the silhouette of a police squad car. I saw the bar on top of the vehicle and easily identified it as a police car. With his headlights on, I would not have known it was a cop car until it drove past me.
I have no idea why two cop cars were driving around Soulard at night without headlights. Maybe the drivers simply weren't paying attention. If that's the case, then I don't think I want those officers driving the streets. If the reasons were tactical, then the reasoning is faulty at best.
If there's another reason I'm not thinking of, please let me know.