Gene, I'd agree that most small businesses don't use Balanced Scorecard. The reason, I think, is that most small businesses use a different planning philosophy than larger organizations.
Large organizations typically define a vision, identify strategic objectives related to that vision, and then plan downward (or outward, depending on how the model is depicted) to realize the vision through the achievement of various tactical and operational goals. As I see it, Balanced Scorecard is a way to integrate and measure progress toward the specific set of Financial, Marketing, Process Management, and HRD goals, targets, and initiatives that make up the vision. The management team for a larger organization can often envision where they want to company, agency, or non-profit to be in two, five, or maybe even twenty years from now -- so they have time (and resources) to establish the related metrics, and to institute the feedback loops (measure, analyze, adjust) that would allow Balanced Scorecard to work well for them.
In contrast, small businesses tend to plan from the bottom up (or outside in). They often begin with a single element -- for instance, a financial opportunity that others have overlooked, a market need that isn't being met, a unique process that provides a radical competitive advantage, or a specialized skill that no one else has. They figure out how to operationally apply that element, then determine how to tactically add on the other elements that are needed to support the operation, and finally figure out how to strategically deliver it in a profitable business context. In one sense, "balance" is built-in to that evolution. Further, once a small business is delivering that initial element, the owner invariably sees other elements and opportunities (I have no data to back this up, but I think most small businesses are actually engaged in a slightly "different" business than their owners initially imagined).
The analogy I use is an oil tanker versus a small sailboat crossing the ocean. A tanker plows through the waves en route to its destination using the most direct course possible, and very little affects it. Because the cargo is valuable and capable of doing enormous damage, certain things must be monitored and measured -- most of which are "internal" to the ship and its well-being (and for which the ship has dedicated equipment and personnel). On the other hand, a sailboat gets pitched and rolled by the waves, and has to constantly respond to changes in the wind and weather. While the destination is (or should be) a measureable objective, a sailboat can't go straight there. So (like a small business), it sometimes has to maneuver to take advantage of opportunities and thrive, and sometimes has to maneuver just to protect itself and survive. A small business "captain" goes it alone, without the sophistication a tanker might have. He/she constantly monitors the "weather" and is always prepared to change a financial, marketing, process, or developmental objective if necessary.
Bottom line, managing a small business presents different challenges than managing a large organization, and therefore relies on some different management approaches. The rewards are also different. Big organizations offer big rewards, but mostly at the end of the voyage. A small business offers small rewards all along the way. If the sailboat passes near that one particular harbor on a day when the weather is fine and there are no commitments to keep, the small business captain can drop anchor and be like one of those folks in a Corona commercial for awhile. (The big tanker just plows on by, while we lay on the beach and wave.)