Consider that we're writing for a visual medium, and answer this: would you rather have one character tell another character about an accident that just happened, or would you like to see that accident unfold on the screen? You can substitute accident for another event, and you still have the same idea. Do you want to be told how two lovers met, or do you want to see it happen?
In my Introductory Scriptwriting course at the University of New Hampshire at Manchester, each student is required to pen a dialogueless short screenplay of one to three pages. There's no better exercise than to write an all-visual script. It's also a strenuous task.
For playwrights, the challenge tends to be how to describe what's happening in the scene. For novelists and even short story writers, the difficult task is often how to reduce the amount of description while writing on the page what will occur on the screen once the script is filmed.
If you want to try this, you might attempt to write a scene between two people who each want the same thing, but only one person can have it. Want more specifics? Fine: Two seven year olds. Twins. One brand new bike. What will each do to get the bike?
Here's another exercise: try to take a scene from a favorite story and write it without dialogue. I'm picturing the fence-painting scene in The Adventures of Tom Sawyer. How can Tom get the other kids to paint the fence for him without using any dialogue?
Finally, stop and notice next time there's a scene in a film where no dialogue is exchanged, yet the story is clearly advanced. Or did the lack of dialogue not work? If not, why do you suppose that is?
Until next time, write on!