Planning is very important in life. Everybody should do planning at individual or family level. As an individual, you should plan for the day well in advance in order to accomplish what is to be done in that day. At family level, a family plan helps to focus on supporting the entire family in its growth and development. Planning is also done at business and organizational level.
Another consideration. Should the business plan be a document that is focused on selling an idea for a product or service? For many years I worked in a company that did not want anything in a business plan that could be construed as showing a bias towards or against a project. The mantra was to only present facts in the business plan. The Operations Research Department was there to review the analysis as being unbiased. To handle the "what if" scenarios or sensitivity analysis we prepared a supplemental analysis documents which were mostly financial oriented. Personally, I like a factual approach and use the presentation of the final document to point out the conservative aspects of the content.