Stupid may be strong, but risky, oh yeah.
All of the outdoor organizations that I have seen recommend a using Ten Essentials sort of gear list, and for good reason. Every year we see people lost, suffering from exposure, injured, or outright dead from lack of preparation and basic equipment.
Every time I go for a hike, I meet people on the trail with not a shred of equipment with them, not even a water bottle. The typical day hiker I see is wearing cotton clothing and no pack, so the most they could have is a pocket knife and maybe a small flashlight, but certainly nothing else. And I see them headed up a trail in the late afternoon, giving them an hour or so leeway to get back to the trailhead before dark. I honestly think they have no clue how dark it can get in the mountains, away from city lights, and you can add forest cover and clouds to make moon and starlight of little help.
Relying on weather forecasts is totally unreliable. Take my day hiker example and add some rain and you have a hypothermia case just waiting to happen.
Most of the victims I have read about aren't deep in the back country. A couple miles into a wilderness area is more than enough to get you in trouble. These are what I call Gilligan Hikes: just a "three hour tour" that turns into a life threatening event. I have my essentials every time I step off the pavement and someone I trust knows where I went and when I am due back.
Navigation is probably the foremost area where some training is needed, although many could learn from a book. First Aid is easy enough to get training and IMHO, it should be covered in all high school health classes. Shelter building is easy enough to learn from a book if the person has basic knot-tying and woodworking skills and fire building should be easy enough to learn. Scouts learn all of these things as a matter of course.
But going for a weekend with no shelter is just foolish. Just a little line and a poncho or a plain blue poly tarp would provide enough shelter to make a rain storm survivable.
How do you motivate people to insure their basic survival? Ask Darwin! I would send them email links to local search and rescue stories. Some of the news links that Eric Chan has posted have been very educational.