@JanetheActuary This varies a lot by departments and even based on who is chair at a given time in a department. In some cases there is a real imperative to keep enrollments, in other cases to match other university/department objectives.

@JanetheActuary Somewhat understandably, professors in larger programs tend to want to teach more in their specialty in smaller classes rather than repeating the same big enrollment classes over and over again.
And of course hiring also constrains teaching...

@JanetheActuary ...if a department doesn't have anyone who does Latin America, well then it probably isn't going to have many Latin America classes on offer, for instance.

@JanetheActuary But in my own experience teaching *quality* can overcome most of these problems. Profs that teach well earn reputations among students that get passed on, year to year and so over time good teachers can enroll almost anything.
But we don't hire much looking for good teachers.