I will hazard a guess and say most (all) of those shown came in that condition to the present collector.
Over the years I've had boxes of common covers. And over the years I've culled through them every now and then, saving those with interest, cutting most into 2x4's for the cancel, and clipping the rest into kilo ware donations.
I think if I had saved all, I would not get in the front door.

pat