In the 2014 American movie, "5 Flights Up," Morgan Freeman and Diane Keaton play an elderly couple who think about selling their two-bedroom Brooklyn apartment. Since they have lived in the unit all their married life, the decision is a difficult one, and the premise of the plot hinges on the reason for their putting it on the market, which turns out to be a simple one: They live on the top floor of a five-story building with no elevator.
As with public toilets and convenience stores, we only really notice elevators when we need one and they aren't there. This becomes a concern for an aging urbanized society like Japan, since many of the residential collective housing structures built before the 1990s didn't have any. The standard design for most public housing, whether it be for low-income families or for the general public through the Japan Housing Corporation (which turned into the semi-private corporation UR in 2004), allowed for up to five stories with no elevators, whether they be rentals or for sale.
Most of the families who bought units in such buildings did so when they were relatively young, and if they still live there they have gotten on in their years and are probably unable to use the stairs as readily as they used to. So, like the abovementioned fictional couple, they may have to move. Unlike the fictional couple, however, they probably aren't going to get a million dollars (¥118 million) for their flat, so moving may not be as much of an option.