That's because those books (very popular in airports) are blog posts extended out into books with almost no value add as a result aside from some "choice" anecdotes intended to prove whatever points they're making. Usually it's the same point people have been making for 4+ decades. The act of reading books like those, deciding to read a self-help book for example, is almost more important than whichever book you pick. Most of them are interchangeable. They're meant to make you think you're improving yourself by reading them. (Dalio is more trying to position himself as master of the universe.)

Actual academic monographs and good novels are usually book length because their arguments and stories (and characters) require that book length to reach their full potential.