That's because paperwork is a more easily-measurable product than other kinds of work. The people who produce paperwork are more easily ranked in a performance review. They tend to rise in rank faster, and promote more people like them.
Also, paperwork is the one item in the universe that seems to last forever. When it's not needed, it's lovingly stored away in vast warehouses like the closing scene in "Raiders of the Lost Ark". When the warehouse is filled, they build another one somewhere else.
I know this is true, because even the city of Detroit does it. It claims to have no real records prior to about 1930, but almost 150 years of records are stored in secret unmarked, unlocked warehouses taken over by the city after the original owners abandoned them. I know this from a friend, who was befriended by a cop, and taken to one of these warehouses, where police records from the 1920s Purple Gang were stored, despite the official statement from the city that the records were destroyed long ago.
If a hick town like Detroit can save all its paperwor, imagine what the federal government can do. And imagine who gets the good job review for handling paperwork.
What are we doing for Valentine's? ;-D