Conflict should be part of every story

Conflict should be part of every story because conflict is a part of every life.
How we react to conflict is a measure of our character so introducing conflict into a story gives us a chance to develop the characters. Think of Archie and Edith Bunker, for example.
Conflict doesn't have to be violent or obvious like a war being fought. It can be a disagreement between two people or it can be rain falling on a family picnic. (How does each family member react to the picnic being canceled?)
If you don't know any other way of introducing conflict into a story, just have one of your characters say "no."