I think there are many reasons people leave the trail. We have just left because I, Tas, tore my calf muscle, but it could have been a dozen other reasons. We hit a 'brick wall' no reason, we are very experienced long distance hikers, but different terrain, different hiking food to our own country, tiredness, etc, etc.
It is important to remember that whatever distance one does, it is their hike and their achievement.
For me, coming off the trail was a mixture of intense muscular pain, frustration and even relief. Walkabout Roo and Tas