There are many reasons for utilizing such a document. Is the final document going to be about implementing a decision already having been reached or is it about analysis and recommendations for a newly proposed activity. As noted above, a finished document may be for internal or external purposes. Externally they are often used to solicit funding for a start_up or joint venture. Whatever the purpose, do not confuse effort with say, a marketing or a production plan.
Some people think that they do not need a business plan for a small business. But let me make it clear that the size of the business doesn't matter. Whether small or big, you need a plan. If you need a plan as an individual and for your family, then why not have a plan for your small business? Like for individuals and families, you need to plan for your online small business. A business plan shows you what you would like to achieve and how to achieve it. Although not all plans are written down, a good business plan should be written down. If you have it in your head, it's high time you spent some time to write it down for better results.