At this point in history, leavened bread was a lighter bread that was considered much nicer than flat breads. There was just one problem: left out in the desert heat for long periods of time, it would go hard and became difficult to eat.
The solution? Toast. It’s likely that toast originated as a way to preserve bread rather than as a tasty breakfast item smothered in butter and jam. By scorching slices of bread, they lasted longer as a palatable food.