When poor people stop spending money, the economy goes into recession. We have buying power.

Poor peoples' spending is less optional...you cannot exactly just stop buying groceries or clothing in hopes that the system changes. "Vote with your dollars" is essentially meaningless...especially when the very same billionaires we're talking about have conglomerated the goods in the essential economies. The food systems and the medical systems are practically cartels at this point. (i.e. Boycott Goya all you want, are you really sure that they aren't still producing your beans anyway under the store brand?)

I also think that the above is a gross oversimplification of what a recession is. The poor have been mostly buying only essentials for a while now (because it's all they can afford with the recent inflation) and we still aren't technically in a recession.

EDIT: I personally think a better means to protest monetarily for the non-well off is actually debt strikes. Most people don't have a lot of spare cash, but they sure do have a lot of debt. Unfortunately, it's another one of those things that only works if a whole lot of people do it at once.