math professors are incentivized to spend years of their lives writing a textbook they can then have their students buy every semester, and thus create a second

math professors are incentivized to spend years of their lives writing a textbook they can then have their students buy every semester, and thus create a second revenue stream for themselves Honestly, they're not incentivized by money. The vast majority of textbooks don't make the professors any money at all. They may be incentivized by the tenure process/promotion at their university (esp. in smaller colleges), but that's an entirely different scenario.