Strategy _ similar to business strategy, marketing plan will capture strategies required to support your business strategy. For example if your business goal is to achieve 20% increase in sales, your marketing strategy would be to 1) introduce new product, 2) increase price for premium offerings, 3) recruit more distributors and offer commission scheme and so on. Strategy is king. When you can see your business in totality, I can assure you that you will find it easier to manoeuvre. Marketing plan is the place to address all these issues.
Imagine if you can do all these and manage all these in a marketing plan? Systematic, organized, well thought, innovative and captured all your pertinent business information, don't you find having a marketing plan is useful for your business?