While this approach is widely used to stabilize operations first, ITIL documents the practices to use for Service Management, not Process Management. Focusing on processes first, with little understanding or development of what services are offered by the organization, will result in short-sighted decisions being made that could potentially become an obstacle later as the organization begins to transform itself into a Service Provider. To overcome this, an organization should at least develop the definitions of services in parallel to the operational process improvements.
By documenting and better understanding the services that the organization provides, the concepts of services stay in the forefront of the improvements and influence the decisions that need to be made during these improvements. This effort will also begin the organization's cultural change from a technology provider to a service provider.
Ideally, an organization should develop their understanding of services first prior to any other improvement efforts. However, this approach usually only works in an ideal situation and most situations are far from ideal. When making operational improvements, keep the end-goal in mind - IT Service Management. Your operational improvements should be consistent with the path to the end-goal and not deviate too far off of the path.