There's lots of ways to steal a little bit from people in ways they don't realize or can't do anything about. Stealing $5 bucks outright is of course the obvious thing; disproportionate overdraft fees or ordering transactions to maximize overdrafts is another; selling something with apparent X% risk and real X+Y% risk is more subtle still.

Information asymmetry isn't a theoretical construct--it's the basis of a lot of different ways to steal from people without their knowing.