There is a difference between blur and soft.
Blur can be intentional or unintentional, but is usually caused by motion-- camera, subject or both. If done properly, it's artistic. If not, it's sloppy.
Softness not the same as blur. In fact, if the subject and camera are still, you'll see that the picture is sharp, yet soft. Softness can be due to the lens (older lenses not as sharp as modern lenses), it can be introduced by a real diffusion filter (eg Softar), or it can be done in PP.
In other words, softness is something one can control. Blur-- very difficult, as it depends on motion and shutter speed.