It could be related to physics, where it's easier for an object to keep doing what it's doing(travelling in a direction etc) than to suddenly stop in it's tracks. That would require some sought of 'outside intervention'.
But science aside, unfortunately the human body doesn't really shutdown unless it's got some form of infection(then there's also sudden death syndrome...).
When you look at it, it takes quiet a lot to kill the body, some people have survived from some pretty horrific accidents.
It's also easier to simply not get help, and let life takes it's natural path(which for most of us, without intervention, would probly result in suicide). Sucks that life doesn't have a 'DELETE' button somewhere...:dry:
:hug: are you on any meds/counselling etc?