I would too, but most people are stupid and the intelligent people have a lot more concerns than that. Plus the psychological effects of safety after periods of intense danger can be very damaging to a brain's capacity for reasoning. Basically keeping your guard up always will keep you safe, but make you go crazy. Letting your guard down, even gradually, is almost like a drug in that it overrides your instincts and thought stronger than it should.
Part of why survival genres are always so compelling. Humans can survive a lot of things, but what happens to their minds in the process is fascinating if not incredibly horrifying.