That’s going to be true of a lot of places, but it is more apparent at universities because there are a lot more faculty, so there are more courses in the system. Basically, this is what happens – any given faculty member might teach a rotation of 5-10 courses (or more). But they might only teach a fraction of that in a given year. Some will come up more often (required courses for the major, gen-ed courses), and electives will be taught more rarely.
The catalog is not the same as the class schedule. Getting a course in the catalog requires a long bureaucratic process, so once a course is in there, it stays – even if the prof doesn’t teach it often, even if the prof who’s primarily responsible for that course leaves, even if they have a very low teaching load, etc. Departments and colleges tend to keep those courses in the system unless there’s a good reason to take them out (my department just “cleaned house” and updated or deleted a bunch of obsolete courses from our catalog offerings because the people who taught them are no longer here, but we haven’t done that in years). The best thing to do is look at the class schedules for the last 4-5 semesters, to get a sense of which courses are offered every semester and which ones rotate less frequently.
Again, this is likely to happen at a LAC, too, but not to the same degree. But even in these schools, professors can go on leave, or get reduced teaching loads, or retire, or rotate through electives and special topics courses, and courses might stay on the books even if they’re not taught.