Local custom and culture may be an important factor as well. Here in SoCal, proper behavior is to keep right on trucking (slowing down will most likely result in a traffic jam) so you had better have your cell phone working. On the major arteries, road side assistance phones are installed at quarter mile intervals

On the other hand, in South Dakota, where I spend most of my summers, we had a minor breakdown right in town and within the space of no more than ten minutes, three strangers approached us to offer assistance without us doing anything to solicit aid, other than to look underneath the vehicle to see what in the blazes was wrong with our clutch linkage.

Folks in a rural setting are more inclined to offer assistance.