Seems like a circular question. Office Space is a movie about work because it specifically defines itself as a movie about work. But when I nominate (as I now will) Apocalypse Now as a great movie about the experience of being a soldier in Vietnam, everybody will look at me funny. As if soldiers weren't professionals being paid to go to work.

Of course, I might be wrong about Apocalypse Now, as I've never actually been an infantryman in the Vietnam War. I have been a science grad student, however, and I can say without hesitation that Real Genius is the Apocalypse Now of graduate school. Even the physically-impossible hacker tall tales in that movie are note-perfect.

EDIT: More examples. Adaptation is very much a movie about being a professional screenwriter. And there are dozens of movies about being a professional cop, musician, athlete, reporter, or artist.