That is the intent of the publishers when they change frequently. If the teacher/professor gets a cut then they might share the same incentive to update regularly.
But at the core from a teaching perspective, the general reason for assigning books that might only have a portion used in class is because the teacher thinks the book as a whole will be helpful in understanding the content. Otherwise they would just recreate their own version of that chunk of information if they aren’t getting a cut from sales.
That is the intent of the publishers when they change frequently. If the teacher/professor gets a cut then they might share the same incentive to update regularly.
But at the core from a teaching perspective, the general reason for assigning books that might only have a portion used in class is because the teacher thinks the book as a whole will be helpful in understanding the content. Otherwise they would just recreate their own version of that chunk of information if they aren’t getting a cut from sales.