I would agree this is a huge motif in Western literature, likely in lockstep with Christian values, but I would wonder if this is not just a Christian value...Immediately I recall the story of Guanyin and Shancai, the bodhisattva who took a disabled boy as her apprentice, although this is a religious story.

Although I also remember that in medieval Japan it was such a pastime to watch people having mental breakdowns as a form of entertainment that it was written into dramas.

To paraphrase Irwin, outside of the city were the wastelands, where only huntsmen and bandits roamed. Although it is outside of the city where many of the more fantastical stories take place, being the place of the greater unknowns. Much more you have people coming in and out of the city trading goods - probably the basis of commerce being a major theme of the stories.

Since you mention it, imagine the untenability of "homesteading" outside the city was a huge influence as well!