Really don't agree with this -- retiree doesn't mean "decrepit". You're still very capable of driving. My own parents recently retired to a rural area in the US, in a neighborhood with other retirees, where they're a 5 minute drive from the nearest grocery store and a 30 minute drive from the nearest "city" of ~20k people.
It's very walkable in the sense that there are sidewalks and parks, but not in the sense of living in a downtown core with public transit access to essential services.
and with a $1M house should have a sizeable 401k specifically so they’re not relying literally on the housing market to retire. Any number of events could cause the same scenario you mentioned.. so I’m pretty much any realistic scenario for most people, tax deferred investments dwarf the small boost you get from buying a slightly cheaper house.
And having more $250k houses now means it’s easier for everyone else to build up a retirement plan.