On Dudley and choice seats for Quidditch

A couple of thoughts from the first couple of chapters of The Goblet of Fire.

After Fred and George managed to tempt Dudley with a Ton-Tongue Toffee and blow his tongue up like a balloon, do you think Harry told them about what Hagrid did to the kid? It would be a natural conversation, wouldn't it? "That was funny what you did to Dudley, but it's got nothing on the pig tail Hagrid gave him four years ago!"

And what do you make of the differences between how the book deals with the seating arrangements at the Quidditch World Cup and how the film version addresses the same issue? In the book, both the Weasley party and the Malfoy family are seated in the top box, leading to that nasty confrontation. In the movie, however, the point is made clearly that, while the Malfoys are guests of the Minister for Magic himself in the top box, Mr. Weasley could only afford the cheapest seats for his family.

That's not the only difference. In the book, Rowling makes it clear that the seats at the top of the stadium are the best and most costly; in the movie, Lucius Malfoy mocks Mr. Weasley's seats which are so high up in the stadium that, if it rains, the Weasley's will be the first to know.

First of all, why change it at all? Second of all, when the sport is Quidditch, the best seats must be at the top the stadium, where all the action is. So why does the movie version make it sound like it's better to be lower in the Stadium? Is that just because most Muggle movie-goers would automatically think lower is better because that's how it works at all of our sports venues?

I don't know. I don't get it. I can't figure out why the movie makers kept changing little things like that when the original book is clearly right.