For one, the marketing planning process allows for all team members (the brand and leadership team with the marketing agency) to set goals and establish buy-in.
This initial alignment allows for the agency to work efficiently and fluidly with clear parameters. Most importantly it allows the full team to define what is being marketed and to whom. It is often surprising how many agencies and their clients alike fail to create and revisit these definitions. It can be common for a company to have a marketing team working under one assumption, a sales team working under another assumption with a leadership steering the ship in quite another direction. This limits success and cripples creativity.
Clear messaging and position document... Get the vision straight! A marketing team needs to create a document that spells out launch positioning early on. This alignment document can help to reduce the common friction between teams, by creating language, value-statements and buyer personas that are used by marketing team members, sales team, leadership team and anyone involved in communications with the brand message. This will allow the team to build a customer segmentation plan for communications and automation.