All projects must have a strategy for success. This is not the strategy for building the product - although that is a must have as well. It is the strategy for the outcomes of the project. It is the set of capabilities that the project provides to the stakeholders.
This is how you separate the value generation of the project, from the earned value of the project performance management. The common notion that earned value is no use in project management, because it does not describe the value of the project to the customer, is of course mis-informed and a bit naive, since EV is not designed to do that.
But this is besides the point. Without a reason for the project, there is no way to actually measure the business value of the project. The notion that agile processes measure business value, begs the question, how do we know what business value we should be measuring and what are the unit of measure of that business value?
This is where strategy comes in. One approach - likley the best approach to strategy and strategy making is the Balanced Scorecard. A good example of this for IT looks like this.
The project needs to answer the questions possed by each of the strategic initiatives in the scorecard. By connecting the dots between the project tatctical activities and the strategic initiatives, the providers of the project value can answer the question why are we we doing this and most importantly what is the VALUE of the things we are doing?