Portraits in the Hallway

The classroom hall of my school is lined with portraits of distinguished faculty, deans, and trustees. All of the portraits are covered in glass. All, that is, except two: the portraits of Richard Posner and Richard Epstein. Their portraits are not under protective seal, but are exposed. Why is that? Is it because they are the only people portrayed that are still alive? My hunch is that the subjects of all the other portraits have passed. Does this mean that at their (hopefully distant) death, their portraits would be encased in glass? Why not just cover the portraits now? Are the portraits exposed so that they can be altered if their subjects change in appearance? If Richard Epstein were to change his sex and go by Rochelle, would that be captured in this painting?