Why is plot important to a story or novel?

A plot is one of the most important parts of a story, and has many different purposes. Firstly, the plot focuses attention on the important characters and their roles in the story. It motivates the characters to affect the story, and connects the events in an orderly manner.

Most often when you read a novel, you are interested in

What kind of people you are reading about. What sort of thoughts they have. What they consider important. What they consider unimportant. What they consider immoral. What they consider the right thing to do.

Plot is the easiest way to put people in action so that you see what the answers to those statements are.