Mrs. Thompson , although I completely agree with your method for new entrepreneurs I find that as the business grows, generates income, takes on more employees, etc a more comprehensive business plan will need to be written to account for the growth phase, and keep the company and employees on track with new goals, forecasts, etc.

Another reason when you might need a more thorough business plan is funding for operating capital, which many businesses, in my experience, struggle with. Many go looking for working capital loans at their favorite bank and must present something longer than a one-page business plan, or risk the loan being denied.