Several new stakeholders are concerned about being asked to review a product demo before it...

The product owner may act as the stakeholders' proxy at the demo and that the stakeholders do not need to be directly involved with the team.

The demo will show whether or not the team understands the level of effort required to complete the project.

The stakeholders will learn whether or not the implementation has worked by getting immediate feedback so they can correct their assumptions for the next sprint.

The stakeholders will be better positioned to evaluate whether or not the resources expended by the organization are worthwhile.