Why does a university course become defunct?

Some reasons we've eliminated courses in my department:

• The professor who created the course is no longer at the college or is no longer interested in the material.
• College-wide requirements have changed, and the course was created to meet a requirement (such as for interdisciplinary work).
• As new courses are added, other courses have to be removed, unless the size of the faculty grows.

In one of the University's that I attended, the Geological Engineering courses were scrapped (and consequently, the entire degree), despite their uniqueness. Having said that, the reasons were valid, which included:

• Drop in enrolments/interest - it already had a smallish enrolment base.
• The expertise the professors had was quite unique for the courses offered, when one left for a more lucrative job and another passed away, they could not be replaced.
• The job market - at the time, there was a drop in employment opportunities coming from this course.
• Reputation - this is an interesting one, the course had many field trips, but the behaviour of many of the students were becoming less tolerated.

All these combined to inspire the powers that be to cancel the courses, and thus the degree in its entirety.

The answers vary. Sometimes there's not demand, not enough registered people for the course, or no professor that can teach it. Courses may stay in the books (the catalog) but don't get offered. Perfect example, my department offers courses in applied probability and stochastic differential equations in the catalog, but it doesn't get taught.

As for your particular course, I'm not sure.

They also can vanish because of restructuring, either of its content, or because of the greater degree changes. This happened a huge amount over my undergraduate degree, as my university did a near complete overhaul, changing many 4 year bachelors degree's into 3 year bachelors + 2 year masters, and adding significant extra cross disciplinary requirements.

2 units may have there content reorganized into 1, or 3 units into 2 etc.

or unit might be appear to be cancelled, but is actually being deffered as it's position in the course structure has changed. For example, something might vanish for a few years, if it was originally a 2nd or 3rd year undergrad elective, but became a 5th year post-grad elective. Which may result from its pre-requisites moving around.

Just to add one more possible reason:

At our department when one professor takes a Sabbatical his courses are usually not offered by the remaining professors.