Making texts that are active is currently a hard job. There is a fairly large set of technologies to know, and an author can worry that each of those will have

Making texts that are active is currently a hard job. There is a fairly large set of technologies to know, and an author can worry that each of those will have a limited life. People who have something to say, and who know all the techs, and who are willing to keep their work up, may well be a small set.