Textbooks

I was talking with one of my professors a couple months ago who's now on sabbatical, during which he plans to write a textbook. Why are textbooks usually so poorly written? He says there isn't much/any money in it, so most people just don't try - not worth the effort.

I gotta tell ya though, my electromagnetics textbook - aweful. According to the professors at SPU, it's the textbook for electromagnetics, but the author never explains or connects anything whereby we could actually learn how electromagnetics work. Everything once covered is assumed to be immediately understood and applicable in any and every way with no explanation within the chapter. Assuming even we could do this, the problems in the book stretch beyond the scope of the chapter, and even the entire book, making it extremely difficult to know or even have any idea of what the author is expecting as an answer.

I have a solutions manual, and even that doesn't clearly depict what is being done; the solutions don't match up or make sense with anything in the text. Textbooks are frustrating and people lacking the ability to teach shouldn't be allowed to write.