According to most baking resources, in order to get the best texture and flavor that is typical of leavened bread, dough should be given a second rise before baking. ... The second rise helps develop a lighter, chewier texture, and a more complex flavor.

Why do you let bread rise twice?

Allowing dough to rise twice results in a finer gluten structure than allowing it to rise once. It results in a smaller crumb and prevents huge gaping airholes in your bread. The reason that you have to let it re-rise is that you just pushed all the air out with the kneading you did developing that gluten structure.

What happens if you only let bread rise once?

Bread can be baked after its first rise, but doing so will sacrifice certain aspects of the bread and you won't get the same flavor, crumb, or texture. You will, however, still get fresh bread even if you do bake it after only one rise.