A business analyst’s role is to facilitate a change in an organization that creates value.
To facilitate that change you need to lead the affected stakeholders from where they are to where they need to be.
Viewing that transition as a journey allows you to map it on a journey map.
What are the steps, how do the stakeholders feel at each step, what opportunities are at each step? These are all questions to help make the journey smooth. They are the same questions you would ask when creating a customer journey map for a client of a solution.