This is the rule I abide by. Even when the scene is your absolute fave but when it does nothing, it probably has to go.
To me here are some reasons why each scene must have its role.
#1 They bog the story
Imagine this you kick a ball, except that it hits onto something and then slows down. That is the extra scene or two. It makes the story less interesting simply because the reader knows it.
Sure many would ignore it, or it wouldn’t affect it. But the story can lose a little of the sharpness or the tightness because of those scenes.
#2 Feels as though it could be used another round or two
This is especially so if it is repeated, and has many scenes which could have been removed and there won’t be a difference. Other than the story being shorter and more enjoyable.
Sometimes less is more, just like how we despise sequels if it is done for the sake of it as compared to say having a real story. And how many best-selling authors either don’t get that much help in editing or is allowed more leeway since their name would automatically sell.
#3 It can be confusing
Especially when the tone shifts are jarring since it can go from intense scene after intense scene, to one which advances the plot. And then all of a sudden they are eating cupcakes.
Not to mention the letdown in the expectations when they go to the end of the scene only to find that it did not have any importance whatsoever. Especially when it’s been preceded by important revelation or escalation of stakes.
So, here are some of the reasons why I stand by the need to have every scene advance the story. In some way or another. Whether it is plot point, action, tension or foreshadowing.