Perhaps the internal fire that drives the hardcore runner is greater then any external source. The competition lies within and it is such a great and integral part of who they are that no outside stimulus is needed.
I think of area runners who I would classify as hardcore. You will not ever find them at races yet if they were to line up, would handily win.
For some, the greatest competition doesn't involve any other person they need to look no further then themselves to find their greatest competitor.