Say you sold widgets – you know, those hypothetical doodads we use whenever we want to talk about selling something without importing the emotional baggage of a particular product.
You sell widgets. The best widgets. Grade A, primo, first class widgets.
Your goal in life is to sell the most widgets possible and thus generate the highest profit.
Unfortunately, the demand for widgets is fixed. Whatever they are, people only want so many of them. But if you could increase the demand and thus expand the market, you would likewise boost your profits and better meet your goals.