In the PADI system of training in this particular topic, they have the wise routine of reviewing any special type of diving course that an instructor wishes to teach that is not on their list of mainstream specialty courses. When approved, they may be used with PADI's approval but are still copyrighted to the writer of the course and they do not distribute them to their other members unless authorisation is given by the writer.
When I first started to promote specialty courses, I came under fire for their obvious nature and knowledge of already experienced divers. Of course, one can learn about "Night Diving" from experience; but who with? And how many night dives does it take from experience with "an experienced mate" to learn what could be learned in a variety of situations? And what other precautions would be necessary for those other situations? Answers to these and other questions can be taught, learned and understood by following a prescription protocol that has, for the main part, been peer-reviewed by a respected diver training organisation.
These courses are often generated on request and for those dive operators who wish to generate more interest in visiting their geographic location. The intent is not just to say "Hey! We have something special here and you can if you wish, pick up an inexpensive (sometimes not!) qualification as a reminder of the experiences you'll have here". These courses can also be used to add to the experience qualification that PADI and other training agencies require for their Master Scuba Diver qualification.
All of those listed below will also allow the fervent instructor to acquire Dive Instructor Specialty qualifications that cover A to Z of the alphabet.