Consider big companies before departmental printers. A memo would be typed and then have to go to the reprographics department for copies or typing pool. Anything more complex than a memo would need to go to an outside printer to be typeset and printed.
So you're looking at hours to days (weeks in the case of technical documentation) turn around time. All the labor was also very expensive.
Departmental printing could cut the turn around time to minutes or hours and reduce the manual labor significantly. This got cheaper and more accessible with desktop printing.
While e-mail is often abused anymore it's much more manageable than the reams of paper even relatively small companies had to deal with just to communicate internally.
