I think you are focusing too much on the negative side of a book you find useless. There is another framing that is more useful and helps to suggest answers to your other questions. One way to think of it to kind of get an intuition for why things tend to be long is to imagine you are going to have someone be your personal trainer for a month. However, they must interview for the job. One interview question you could ask is do ten push ups. That is like writing a short book. The other is run a marathon. That is like writing a long book. What sort of implications come from that? You start getting a lot of filtering criteria and you start to realize that the requested length actually makes the filtering of fit from non-fit much easier. Even better, in cases where you get it wrong, the mere fact that they had to put in enough effort to fake worthiness as the fitness coach required a level of fitness that made them a little more qualified for the task then they otherwise would have been.