Planning is hard because...

Planning is hard because it’s inherently different from other exercises your organization takes on. Rather than focusing on day-to-day execution, it requires a large number of people to think about a variety of possible futures, align on one single future, and then plot a concrete course to get there. Taking this on for your own personal goals (for example, a New Year’s resolution), feels challenging enough — doing this with dozens or thousands of people can feel nearly impossible.

You can’t expect the organization to “just know” how to pull together a quarterly plan. Working without an agreed-upon framework can often be a recipe for disaster.

Source: The Secret to a Great Planning Process