Reviewing the business plan can also help you see what goals have been accomplished, what changes need to be made, or what new directions your company's growth should take.
Simple - the business plan is the blueprint for your business.
You wouldn't walk over to an empty lot and just start nailing boards together if you wanted to build a house.
Having an up-to-date business plan gives you a much better chance of getting the money you need to keep operating or to expand.
Investors and financiers are always looking at the risk of non-repayment, and word-of-mouth is no substitute for written facts and figures in a properly-prepared business plan.