Firepower - some of us developed these habits while eating out in uniform. Anyone in any kind of emergency services or military uniform is a prime target when the action starts.
koolminx - Seating yourself so that you can have a good view of your surroundings does not imply a desire to engage any miscreant who starts something. It may be much harder for you to understand that priority #1 is to survive, even if that means not engaging. And for most of us, being able to get our family out of the kill zone supercedes any concept of heroic engagements. But then, most of us don't have the advantage of exuding an aura of badness that will make Chuck Norris and Vin Diesel belly crawl out the back door when we walk in either.
G-Man, as BikerRN pointed out, you need to refamiliarize yourself with the color code, preferrably Jeff Cooper's version. But you did bring up a good point about practicing watching your partner's six. Of course, that implies your partner is someone alert and aware enough to spot potential trouble at
your six. Unlike my ex who doesn't pay much attention to anything more than 12 feet away from her "bubble".