A professionally created business plan is still the best way for entrepreneurs to clearly model their business and present their ideas in a succinct and winnable manner. The truth is, that while many financial institutions say they don't need a formal business plan, without your ideas being on paper, it is hard for a lender to get buy-in with their risk managers when dealing with start ups and small to medium sized businesses.
Seriously, without a professionally prepared business plan, you are missing out on these benefits:
Having a business loan approved
Developing the next steps for your business ideas
Taking your existing business in a new direction
Reaching the targets you've set
Creating an effective strategy for growth
Determining your future financial needs
Land that angel investor or Venture Capitalist funding