Referees are part of the scientific community and influenced by the opinions in this community. Classification systems are made from yesterday s concepts of the dominant paradigms. There is no easy way out. It is impossible to predict the future scientific, technical and social developments. Every classification will sooner or later become inadequate because too many subjects are failing in it.
New subjects emerge from developments in sciences, but also from sociological changes in society.
Which subjects are dealt with in classifications depends on the literary warrant, bul also on the question which subjects are en vogue in the social environment of the builders and revisors of the classification. This changes with time. Reasons for the changes in interests are scientific developments and changes in social reality, but also fashion and serendipity. Environment was not a important subject 25 years ago. Super conductivity was a very important subject for some years, but the interest has diminished since the great breakthrough did not come.