When I was a student I never understood how something like this could happen. "Just rewrite it" I thought, how hard can that be. But working in a corporate environment I now totally understand it. Everything you write will at some point become part of code that, to the fast majority of colleagues, will just be a black box that they've never touched and don't intend to. Despite my urge to test and document everything, I've already more than once complained about my own code, only realizing later that I wrote it myself. Often you can still find out what it does, but the "why" gets lost and because of that people are afraid to change it.