This point of view implies a belief in a level playing field. It's really not. The system is rigged against the poor. They have the highest interest loans. They're more apt to incur overdraft fees. Sales tax has a disproportionately negative effect on the poor. They are the target market for predatory loans -- adjustable rate mortgages, payday loans, buy here pay here junk auto dealerships, rent-to-own appliance shops, for-profit universities... they're all intended to push their customers into default and to indenture them for life. Sure, falling for these predators qualifies as a poor decision. But it's not hard to imagine the circumstances one might suffer that would drive him to pay $3000 over time for a $500 car when no one else will offer a loan -- a car which now needs $2000 worth of repairs, and now you need a pay day advance loan to perform those repairs, and it easily becomes a torturous cycle of self-perpetuating, crippling, high interest debt.
I don't know whether you agree with Reaganomics or not, but the fundamental justification for tax breaks for the wealthy has always been that they will create more jobs and give more raises, letting their good fortune trickle down and putting more of their wealth into circulation. If what you say is true (and it absolutely is), then how can anyone expect trickle down economics to work? (It absolutely doesn't.)