The Purpose of the Sprint Review
Suppose you want to have a book written. You are looking for a good author and you have a lot of conversations with him about the subject, so that he gets a good idea of what should and what should not be in the book. As soon as the author has enough information, he goes to work and after a year and a half the book is finished. The writer gives you the book and you start reading and then you discover that it contains a lot of falsehoods. The result is that large parts of the book have to be rewritten. If you consider such a situation, would you not prefer to see the author every two weeks so that you could see what he has written in those weeks? So that you could correct him (= have control) is needed that way? That is exactly the reason why Scrum has a Sprint Review at the end of every Sprint; a possibility for Stakeholders to 'control' the outcome of the product.
The Sprint Review is not just a "Demo" or a presentation, it is a collaboration of the Scrum Team with the stakeholders from the business. It is an event with a lot of interaction between stakeholders and Scrum Team in which the latter demonstrates what they have been working on during the past Sprint. The involvement of the stakeholders is highly appreciated by the Product Owner and the Development Team, as it helps them make decisions regarding work for upcoming Sprints and provides them with additional information about the business regarding context, backgrounds, problems, method, needs, etc.
It is good when the business is happy about the solutions offered, but the team also likes to hear other experiences from the business (even if they are less positive). And if stakeholders do not agree with the order of the items on the Product Backlog, that may be said. So as a stakeholder you can be critical and make yourself heard, the Sprint Review is ideal moment for that, because then it is possible to have a discussion together with all the stakeholders. And together you can make agreements without having to organize separate meetings. This way you achieve the best results for the organization together; the business indicates where the opportunities, problems and needs are and the Scrum Team commits to work on the best possible solution.
So, the next time that you are invited to join a Sprint Review, don't ignore it. Go and help the Scrum Team helping you.