Writing is a lot of work. A lot of tedious work. It isn't enough to have expertise in your area: You also need to know how to write well. How to be concise when

Writing is a lot of work. A lot of tedious work. It isn't enough to have expertise in your area: You also need to know how to write well. How to be concise when needed. How to explain concepts in ways that a learner can understand without forgetting things that would make the concept confusing, even though it is basic stuff to you. You need to be able to edit or pay someone to do so. Blogs are easier, but most folks run out of steam after a short time unless they are also good at planning and think in the long-term. Novels and full-length books are similar: Most folks overestimate how long it will be and/or plan it out poorly. And to top it all off, a lot of folks dislike writing, and need (monetary) persuasion to do such work. I'd personally rather make art (my hobby) than to write about it, for example.