There's already enough mumbo-jumbo in the world about strategic planning, so I'll keep this short. If you're dealing with any of the following, consider your company in need.
1) Nobody says, "No." Every idea is met with, "That sounds great! Why don't you run with that?" When you have a plan and people internalize it, there is liberty with saying no (and empowerment) because the team knows what you are (and more importantly, are NOT pursuing).
2) Managers don't know how to make decisions. If they're capable of making decisions (that's a separate skill), but cannot, it's likely because they don't have clarity on vision, broad goals, and how they fit in. It's time for strategic planning (or revised communications on your existing one).
3) Everyone comes to the top person for decisions. (see #2)
4) New week, new idea. If you're in a company who exists based on rapid product development, fine. But otherwise, remember that flavor of the week is great for ice-cream, but not so for business. Employees can't be jerked around constantly with the latest product/service/marketing/sales/tech idea. You need strategic planning to wade through needs and opportunities, make your priorities, and establish the means to deal with the random ideas when they emerge.
5) Initiatives don't stick. Likely, they didn't tie with strategic priorities and/or no one knew what those were. Don't repeat this. Get everyone on the same page. Do the planning.
Be honest. Do any of these sound familiar?
It's easy to ignore these signs, but that catches up with you and the business. In each of these situations is opportunity: empowering people to make decisions, nurturing leadership across the organization, doing the most important work better. Seize the opportunities. Do the planning. It won't lock you in. Planning frees you because it brings understanding and focus, which let everyone do their jobs and do them better.