That was my experience, too. Opposing the racket was a reason that a couple of my professors wrote their own textbooks. Only a few did that, but a lot more wrot

That was my experience, too. Opposing the racket was a reason that a couple of my professors wrote their own textbooks. Only a few did that, but a lot more wrote and distributed their own problem sets so that students could use any edition of the assigned textbook, or even a different textbook if they had one from another school.