I see day hikers on the trail with no equipment an a regular basis. I see them in cotton sweats and flip-flops, no water bottle, no backpack or fanny pack, nada.
Every year there are stories of unprepared folk who were going for an afternoon walk and got themselves in a mess--- what I call "Gilligan hikes ." The evening news has a clip of the haggard sunburned victims being led to the trailhead by SAR wrapped in a space blanket.
The other common report is about an "experienced" hiker who is overdue and assumed lost. Many times it turns out that they are experienced at walking a well defined trail, but have no navigation gear or don't know how to use it, and are clueless to basic survival technique. They typically get themselves totally turned around and end up miles from their intended destination with no essentials. The scary ones are those who don't tell anyone where they are going and are usually located when a ranger finds their vehicle at a trailhead, giving SAR a place to start.
There was an incident a couple years back where a hiker who was a state patrolman and military veteran who got lost on a winter hike very deep in the Cacades. He also forgot his tent and nearly died of hypothermia. Why someone with disaster and military training couldn't improvise a shelter and build a fire is beyond me.
I was walking the Monte Cristo trail one day to find a couple who were lost. The "trail" is an abandoned road. They wanted to be on a trail on the other side of a river which they crossed to get to the point where I met them. In other words, with map in hand, they took a 90 degree turn from an obvious trail, crossed a large river and ended up on a road rather than a trail, with all clearly defined on the map.
To add tothe story, he was wearing a frame pack with an extension and loaded to the top. His wife was wearing a small day pack. He was overweight and pouring sweat while hiking on a gently sloping road. I directed them to the forest service campground at the end of the road. He said he would probably go to a lake high above the campground that he saw on his map instead. I feared for them.