Your reasons are very similar to mine: http://akkartik.name/about http://akkartik.name/about. A. Backwards compatibility considerations. B. Churn in personnel

Your reasons are very similar to mine: http://akkartik.name/about http://akkartik.name/about. A. Backwards compatibility considerations. B. Churn in personnel. C. Vestigial features. Awesome! Comparing the two, I merged your 2 and 3 into a single reason, considering both as cases of environmental change. In its place I have a new one: changing personnel causing evaporation in system knowledge. Did you consider this? Now I think about it, maybe it overlaps with your 1 (my C). So the final mapping is perhaps: 1 <-> B, C 2, 3 <-> A