Then there are the moments when something seems to be going wrong, when one or more areas of the business just don't seem to be working. Cash flow is anemic or the marketing message is flat. Perhaps customers have shown a marked interest in only one particular product or service, ignoring all your other offerings. This means it's time to revisit your business plan, more precisely it's time to revisit the questioning process that helped you craft your plan.
Besides, your friends may be 100% behind you in your new venture, but, in case you are hoping to involve others who have actual money to invest, you may need to be able to make a convincing case. Wouldn't it be nice to have anticipated possible questions and be ready with plausible answers? If you are risking your own money, that is perhaps even a stronger reason to do some indispensable planning.