I believe that rationality is useful for everyone, but maybe the specific way it is presented on this website or how I present it to other people, is attractive only to some kind of people, and may repel others. It could help explain why some smart and rational people are not interested in LW.

Another reason is that rationality is usually less economically valuable than subject-area learning: reasoning from first principles is a LOT harder and less reliable than looking up how something worked last time. Rationality is helpful for identifying and removing cognitive biases, but so is specific experience. Exhaustive study of rationality does not confer magical ability to reason much beyond existing experiments/examples. Thus, for a well-read, well-informed person (the kind we want here), usually they can do just fine by copying what worked for other people they know or read about.