Why is conflict necessary in literature? Give at least two reasons.

Conflict drives plot. without a conflict there is no plot. unless the protagonist overcomes some sort of obstacle there is no story. From conflict also comes the themes of most novels.

What would the themes of Gatsby be if Daisy has taken him quickly when she was younger? Without his struggle to becomes rich in order to be worthy of the girl he loved, there would be no Marxist theme behind the story and the narrative would have been a boring day in the life account of some guy in the 1920s.

It's also through conflict that a character arch is achieved. You first meet the protagonist in his daily life, he encounters an obstacle or conflict (whether is be against society, nature, or himself. He stumbles to find the right answer to overcome it. He fails. Tries again. Learns something about himself through the conflict and triumphs at the end (unless we're reading a tragedy).

Conflict is one of the most necessary plot and character devices in any kind of writing (except sometimes poetry)