What's the point of sprite atlases?

With the sprite packer I can pack several sprites into one atlas giving performance optimization and I can still use those sprites with drag and drop in the inspector.
With sprite atlases I have to reference them by code giving me extra steps to get a sprite out of the atlas. So why should I use it? Is it better for performance? Do I only get the all sprites in the atlas have the same settings feature? Isn't sprite packer better?