Wherever there is dialogue, there is understanding. And, wherever there is understanding, there is peace. As long as we talk to each other, we are not killing each other.
This is true in any human relation. Whether it's at the highest political level, or at home with your partner in life, dialogue leads to understanding. It's a crucial part of life.
As a result, dialogue is a crucial part of writing too. We are, after all, writing about life in its many forms.
You don't have to use dialogue in your writing, but it helps make your writing dynamic in a number of different ways.
Generally speaking the principle of dialogue is to create a polarization. It allows you to illustrate differences of opinion and position your characters in the story, or to seek common ground and create alliances.
To put in another way, a dialogue can either split your characters apart, or bring them closer together. It's a strong dramatic tool with a lot of inner dynamics.
Find your balance
Having said that, you don't want to overuse it (unless it's part of your artistic concept to do so). If your story was a dish, you would want to balance your use of dialogue as somewhere between a main ingredient and a spice.
It varies from story to story, and writer to writer, and part of finding your voice is exploring your use of dialogue.
Personally, I use it a lot, but in order for it to work, I have to mix it with the other elements, so the story isn't a lot of dialogue about nothing. The key for my voice is to make sure my dialogue is always about something of a reflective nature, and I bring that something in from the other elements.
That's me, and you should be you.
So in this exercise you are going to practice writing dialogue, which, of course, belongs to the air-element. We move air when we speak.
The exercise is this: