A poorly calibrated sense of self preservation. Plus it's a pretty foreign concept, it's hard for someone to evaluate the danger of such an abstract premise that is unlike anything else they deal with in life.

Indeed. In that case it sounds like natural selection to me.

Same reason people might want to visit Chernobyl or Auschwitz (I've done both and NK was on my to-do list until recently).

Morbid curioisity about some of the stranger and darker places in the world. Some people want to experience negative things as well as positive, as it seems necessary to get a full picture of our place on this planet.