On old family pictures many of them have scratches, water spots etc. So picture of a picture you are getting the defects of years. With the negative there may be age defects but you have a chance of getting a picture without cracking or other defects.

I bought the cover for the V850 to help keep the dust out. It is meticulous scanning and making sure there is no dust, but can be rewarding.
For instance, most of the pictures I have before the 1960's are small prints. Many of them are small and contact prints. All the pictures I had of my Grandpa, Mothers Father, were small and couldn't tell really what he looked like. It was good to scan a picture of him and see him on the 32" screen.