There are bicycles with three wheels. There are also electric bicycles with three wheels. They require neither effort nor balance to ride, make a rather large part of the city accessible if proper infrastructure exists, and they have storage capacity, e.g. for groceries.
I don't see any elderly people using them. Nice thought, but I am not convinced.
How many elderly people do you see at all? If you think about it, you might realize there are several explanations other than "nobody uses those things"
I live in a big city, so I see a lot of elderly people. But especially the ones who are not mobile anymore you probably see less. If they were using those tricycle things, I would certainly see them at least some times.
My mother uses one.
So one out of several billion elderly people. Nice, but not really a proven concept.
My father used to be a doctor in a place that got converted into a pedestrians only area, he reported that a lot of people had issues. Business for other shops also declined.