"Help them out of a ditch" describes a very common hazard of early automobile travel. The expression probably doesn't predate the auto by much, since a horse (or other animal) team seldom would drag you into much that they couldn't drag you out of.

Automobiles lacked the "horse sense" to stay on the road, and on early rural roads washouts, ruts, and other hazards to navigation quite often rendered one immobile. It could quite often be necessary to seek assistance; but "helping someone," particularly a stranger, with a "temporary predicament did mean that the "local" had to interrupt work in progress, often hitch up a team, (sometimes catch them first if they were out to pasture,) sometimes travel a ways, and quite often go home covered with your mud.

Some would almost always do it willingly; some would do it, but grudgingly. Some would always have an excuse. ("Zek'l up the road a way has a lot better team than mine." etc.)

A common implication was that the person would help with things that were "not their problem," although whether that's an included meaning depends largely on the state of mind of the one(s) using the term(?).

A slightly different shading was that the person would be willing to help you even when you'd done something stupid, like driving yourself into a ditch. (i.e., was not judgmental about helping, or about picking whom or when to help).

John