They were pretty clear with the job for Office Space, they worked for a bank/financial institution and had to update the software for Y2K so the years could accommodate 4 digits. That's why they were able to take push an exploit that allowed them to keep the rounded penny in a transition for their scheme, which may or may not have been inspired by Superman III.

They sold paper at Dunder-Mifflin? It was pretty clear

The premise of Office Space was that they were correcting the Y2K bug. And this description of a small, over-managed, haphazardly administered IT company is a very sincere reflection of how the industry functioned in the 90s. The punchline at the end - where you've got Ron Livingston shoveling asphalt with zen satisfaction while Diedrich Bader shakes his head in disgust - really does sum up the Dumb Guy attitude towards bullshit-but-ultimately-pretty-cushy office work of the era. But I wouldn't say they were doing nothing.

The Office was a reflection of dying backwards industry - in this case, the paper industry in Midwest Pennsylvania - that attract a certain assemblage of idiots and assholes and failkids in its waning days. This was more a story of a historically productive industry dying out.

American Psycho is much more about the Wall Street peak of power and the sadomasochistic personalities that populate it. I think its more comparable to Fight Club, in so far as it's a story of someone driven insane by the higher end business world and left to discover how thin the veneer is between civilization and barbarity.