Simplicity has often been attacked as a yuppie movement with no relevance to the poor. Certainly I would never give a talk to poor people about how to simplify their lives! The poor are trying to survive, and that's not what living simply is about. Simplicity is about making conscious choices for the well being of people and the planet, and poor people don't have the luxury of choices. (Ironically, of course, the planet is less harmed by poor people than by richer people who use up so many more resources.)
However, the concept of Simplicity is vital to helping poor people because Simplicity's underlying goal is to "put money in its place." People are impoverished because of the greediness of the rich.
It seems to be basically a promotional article for the book Slow is Beautiful, but it does look like the main thrust of this author is voluntary simplicity in the service of benefiting the poor rather than for the benefit of the environment, which is what I see most often these days.
I'm going to subscribe to the newsletter for a while to see how the purpose manifests itself in their articles.