Im not really sure whats so hard to understand.
Info can be retrieved but with work, work that can be avoided if nothing is deleted in the first place.
Archieved sales are useful to both sellers and buyers who can check to see what going rates are, what prices would be good to move something if you wanted a quick sale and finally useful incase a despute is created.
How someone can get confused with that is beyond me.
"Its only a little bit on fire"