Maybe your heroes need to do some Impressive Stuff so they will be noticed by higher-ups. Maybe they need to know each other better before they do something important. Maybe you're retelling a fairy tale and it's got trebling. There's a lot of things where you need stuff.
And you need to invent it. And the events have to be different enough to keep your readers awake. And they have to build up to a climax. And it has to fit into the rest of the story. Interlace, even. Though you can invent your stuff and then get the rest of the story to interlace with it.
John Gardner observed of writing exercises that they are much like a writer's normal life because often you are writing something not for its own sake but to make something else convincing. True but -- sigh -- particularly annoying when you have to invent whole scenes.