Starting with the desired business results ensures that we drive to only those requirements that directly support true business value.
First, it is an exercise that really puts into perspective the purpose of a business model (results). This exercise is not only useful to the project team but also the business stakeholders.
Second, it is an approach that can help you justify why certain existing business activities are not being carried forward in the new business solution.
Third, taking a business results oriented approach enables your project team to be more successful at focusing on the right business requirements and not wasting time on capturing requirements for non-value-add activities.