nate river is l
why does the anime have different scenes than the manga?
The closest I've ever come to answering this question is this: the anime needs to "flow" more smoothly than the manga. Manga and anime are two different mediums. For instance: an oil painting would look different if it were copied in charcoal. The anime needs to connect the dots in a smooth timeframe, while the manga has more room to jump around on as many pages as it needs to get the end picture across.
The audiences are also often different. Anime (when aired in the USA, at least) needs to be more "child friendly" (this is why
Death Note airs in the USA at midnight) because children are more likely to watch a program that their parents are ignorant of. Whereas, if the parent bought the book, they probably looked it over and have some vague idea of a plot.
Manga is often more complicated and more orientated to older audiences, and thus can contain a different level of violence, swearing, or sexual content.
You're also looking at one person's interpretation of a story, so what they think is important may not be so to you.