Billionaires aren't the unlimited money piñata that you might hope; their total assets are less than federal yearly tax revenues, and good luck getting even a tiny fraction of that per year. As for corporations, I assume you're proposing raising the corporate tax rate -- but we're already near the revenue-maximizing peak of the Laffer curve on that particular tax, and there's just not much room to get more money that way.

(Also, only about a third of the incidence of corporate taxes falls on shareholders, with the rest being split about equally between lower wages for workers and higher prices for customers. It can be surprisingly regressive!)