It's a classic problem that occurs a lot in software engineering. Somebody or a number of people put together their code and don't properly comment or document what it does, how it does it and why. These people then leave the project and whenever a new coder has to use the code it might involve some guessing on the new coder's part and a lot of "that will take too much time to fix or rewrite" on the manager's.

Actually... this problem occurs a lot anywhere. Look around the room you are sitting in. I'm sure there is something there in the room you've been meaning to do but haven't because meh you'll do it some other day.