My mom volunteers for Meals on Wheels (http://en.wikipedia.org/wiki/Meals_on_Wheels), and a lot of the people they deliver to are in decent enough health, but just sort of trapped in suburban apartment complexes. They end up surviving through a mixture of charities like that one, and relatives who drive them around and bring them things. But many end up moving to assisted-living facilities after a bit, even though they don't truly need to live in a staffed facility, because the logistics of living in suburbia without a car are just unworkable, and they either don't know about or can't afford a more walkable area to move to.
Also, because Medicare covers nursing homes for people who can't take care of themselves (considered a medical expense) but not the lower-key assisted-living facilities (considered a residential expense, and more likely to be abused), people who run out of money when living in an assisted-living facility may be forced to move prematurely to a nursing home, if they aren't able to go back to living on their own. That ends up both worse for them and more expensive for the public.
Just as an example: blind people can't drive at all, but they can walk miles pretty easily and safely. And visual impairments of various sorts are, IIRC, the number one disability among the elderly.
Slower reaction times are similar: they destroy the ability to drive, but they're not a huge deal for walking up a flight of stairs.
I don't see many people out in wheelchairs either, and I agree accessibility for them could (and should) be improved. I do see quite a few people with walkers, though.