Typically, a person likes to be on his or her own, and to lead. Entrepreneurship is a process of new venture creation. It's also a process of creating a lifestyle with which you're comfortable. Successful entrepreneurs must learn how to work in a team environment. Many entrepreneurs are in their mid-30's when they start, and money is an issue, of course.
Cash flow is a concern both to live on personally, and to keep the business going.
An idea must be coupled with an applicable market opportunity. Just having a product or a service does not make a business. Then, there is an evolutionary process. At first, everyone does all the tasks at a new business. The founder can take it to a certain point, until he realizes he can't do everything and needs to bring in professional managers.