At a fundamental level, stories are about conflict. Every story on earth needs a plot, and a plot cannot exist without conflict. I challenge my readers to think of a story that doesn't - you won't find one - at least not a good one.
Conflict makes a storyline interesting. Humans being social animals compete with one another for resources and status. So even at the most basic biological level, conflict is what arouses our interest. At a basic evolutionary level, we weigh the social costs and benefits of everything we do.
This is of great importance when developing your characters and your plot in a story. Given that most of the characters you create will have at least some human-like traits and your target audience will as well then appealing to this primal instinct can really help draw the readers in.
As an avid reader myself, one of the most frustrating things for me is when nothing seems to be happening in the story. I can't tell you how many times I've flipped forward in a book after a few pages of mindless blather where the author just likes hearing themselves talk. If your reader does this, they're not enjoying themselves and they won't come back.
If you've ever flipped forward in a book, you know why you did it: You're Bored. Fantasy writers are especially bad for this because not only do we have to tell the story we have to tell the reader about the world the story is in. It's one of the reasons I try and introduce conflict as soon as possible in my books - sometimes in the first sentence.
The sooner the reader knows whose side they're on the better. In my view, every word that you write should be built around the conflict in some way. No one cares what magical creature the mountain looks like or that the air smelled of dew and rose petals unless it helps to move the story forward. As a general rule, I try and keep my worldbuilding descriptions down to no more than a few short paragraphs as it keeps the story moving and short paragraphs are easier for the reader's eyes.