I have to chime in here on Tom's side. Most groups aren't that well organized. What constitutes easy, obvious terrain and signage varies tremendously with experience level. We had an epic search for a young lady who was gathering firewood at a campground, got out of sight of the group and wound up walking about seven miles down a canyon, spending a stormy night out on her own, lacking about twelve of the ten essentials.

I think some people trust in the group and don't pay attention to their surroundings and landmarks - something inadvertent happens, and they are figuratively and literally lost.