If you're busy clearing debris from the road and talking to other drivers about your fender bender, your phone is likely back in the car out of ear shot.

I'm not sure why you think questioning the default-on status of this feature is somehow an opposition to its potential usefulness in the extremely rare times you're unconscious or pinned AND nobody else is around to call. I mean, this article is about the phone calling emergency services from roller-coaster rides, which says it all. It should default to OFF. You have purchased an i Phone not an i Emergency Beacon.