This "mythical flowers by the roadside scenario" comes from my actual life. Every time I drive to the gym, I drive by an older gentleman who sells flowers on the roadside (seasons and weather permitting).
It sounds like you have a problem with the Walmart corporation itself, not with an old lady who chooses to spend her time greeting people there. I also see a lot of negative that comes from money-hungry corporations that make terrible products through bad overseas working conditions, and I myself choose to shop at Walmart as little as possible.
Retired folks, by definition, don't need good money; that's why they're retired. Many times they just wanted something to do with their newfound time. I never said that Walmart "replaced community." The Walmart greeter I am thinking of was still active in her church as well, and very much a part of that community.
I still can't believe you haven't met a retired person who got a part-time job just for fun and for something to do with their time. Retired people also volunteer all the time; do you consider this "slave labor," since they are not paid, and their work benefits someone else?