When I ask entrepreneurs and small business owners, it is not unusual for not having any marketing plan. I once read that Sir Richard Branson never had any marketing plan when he started the 1st Virgin business many years ago. In fact in one study of entrepreneurship (I couldn't recall the name of the study) was that as much as 50% of entrepreneurs and business owners don't have a business plan and marketing plan when they first started the business.
Corrective Plan. A marketing plan is a living document. Trust me, the moment you have it and experience planning your marketing, you will realize this. Therefore it is a plan that allows you to assess past strategies and results and at the same time allow you to make necessary corrective measures to fit your business growth. for example, who expected the 2008 financial crisis to hit us so badly? No one other than the few so called "economists" but how did responded to it? Severely. Many businesses closed including many giants. But the good thing is, many have a solid marketing and business plans, therefore they make quick corrective actions and moved forward.