Agile Scrum is made for the projects, where requirements are rapidly changing. And making a long term plan doesn’t make any sense.
Iterative development means iterative learning and implementing the lesson’s learned in the same project and NOT in the next project. Iterative releases means value for the investment being made by the sponsor at early stages; rather than waiting for completing the entire project- and taking a big risk. Early release of high priority requirements will add business value to the customer. The product will have competitive edge over other products available in the market. Development team can focus on smaller part (features / requirements) of the project and completing them; rather than having too many things in their plate.
Not only that, adopting latest / cutting edge technologies, getting continuous feedback from the users are added advantages of Agile-scrum.