Creating soft and even lighting

In a perfect world, you would set your flash on it's stand, click the button, and soft even light would cover your subject in all it's glory.  No accessories needed.

We don't live in that world...

Image captured with no modification for a harsh, edgy look

Flash accessories will make your photography look more professional.  There are times when you don't necessarily need to use them, but most images could be drastically improved through the use of flash modification.