There’s no profound reason why authors don’t typically include solutions. It’s not gatekeeping and it’s not to appeal to an idealistic sense of the Right Way to

There’s no profound reason why authors don’t typically include solutions. It’s not gatekeeping and it’s not to appeal to an idealistic sense of the Right Way to learn mathematics. The real reason is twofold: 1. Authors write textbooks for universities and professors, not students. They write for the academic paradigm they’re familiar with, in which the professor is primarily teaching a student. The textbook is simply used to arrange a course, and professors would rather not have solutions available in the textbook. 2. Authors don’t earn much money from textbooks and textbooks aren’t weighed very heavily for tenure. There isn’t much of an incentive for them to write textbooks with solutions for the reason stated above, and it’s actually significantly more work to include solutions to your exercises. To put it very bluntly, there are extremely few non-students in the market for math textbooks, which is already a high-effort and low-return market for authors as it is. To get such a textbook you’d need someone who: knows the material extremely well, is very good at exposition, has a lot of time to invest in this as a passion project and doesn’t mind if it’s not used much or at all in well-known universities.