Traditionally, projects were focused on the production of a number of deliverables. Project success was measured against the triple contraint of scope, time and cost: finishing on time, not exceeding the budget and delivering the scope according to its quality specifications.
It has been repeatedly proven that this approach is not the best one. Many times, even if the perfect deliverable is created, it is simply not used. Or, it is not the deliverable that should have been created. In other cases, it is not the deliverable that the customer had in mind. Therefore, no benefits are received and no value (defined as benefits minus costs) is created from the project.
So, in order to be able to get some value out of the project, the focus should not be merely on the deliverables, but on the benefits. This is a realization that gradually becomes clear, and thus the management of the project starts to look at the business justification issues too!
In practice, this means that before starting any project, someone, somewhere within the organization, must look at the balance between benefits, costs and risks of the project. If this balance looks good, then, and only then, the project should be authorized in order to proceed. Moreover, this balance must be checked throughout the project so that the project investment is justified.
As a recent example, the last of the A380 super airplanes has been built... even if it is a wonder of engineering, this airplane failed to sell much more than 280, when its initial business case was for 750... Thus, we might have had a perfect deliverable in terms of technology and engineering, but no benefits were achieved...