It's a good slogan to try to educate people to pay attention to their surroundings.
Theoreticly, the only time a person should be in condition white is when they have set physical barriers up to protect themselves. (at home with doors locked and alarms/dogs set) But people are human so they make mistakes and let their guard down.
Some folks don't want to put forth the mental and physical effort to stay alert and in condition yellow when they are out and about. These are the grass eaters and airhead soccor moms who have their eyes down and get into trouble.
Some folks stay in condition yellow and keep their eyes up and scan, with an occasional lapse because they get tired or distracted. These are the meat eaters. By knowing when they are in a higher vs. lower risk envionment, they manage their alertness level and know when they should be scanning and when they can relax a bit.
If you are carrying a gun, you really need to be a meat eater, keep your eyes up and be alert every time you go out.
Gringop