There were some situations in which having someone keep watch while everyone else slept was the smartest idea. After all, if everyone was asleep then if something came by everyone would be screwed. While it helped if the person playing overwatch was known and trusted, sometimes you just couldn't be too picky. "I might take you up on that offer... You wouldn't happen to come somewhere out of the sun that I could get some rest for free would you? I'm afraid that the hardship that drove me from my home has also left me without anything but the cloths on my back."