Why are black cats not adopted?

The reasons why black cats are not adopted are because people find the coat plain and boring and the black cat has an association with bad luck and even evil.

The black coat is relatively uninteresting to the average person. Clearly many people like black cats but on average people find other coat types such as tabby and white more interesting. The black coat is too plain to some people. It absorbs light so it is harder to see texture.

Perhaps the biggest reason is that the history of superstition that has been carried forward to the modern day. In many places, the black is considered bad luck. Yet in many other places it is considered the opposite: good luck. That tells you how irrational the idea is. But it is real and it puts some people off adopting a black cat.

Then we have the idea of a witch's familiar and the night and darkness etc. Black cats are associated with the night and therefore with the unknown and evil etc.

The night or darkness makes people nervous. The black cat has this loose connection to the night.

What people don't realize is that the genes that make the cat black also makes the cat more resistant to disease. This last point has not been thoroughly investigated so it is somewhat anecdotal but the research that has been done supports this conclusion. And it applies to wild and domestic cats.

Perhaps this is a factor that would rehabilitate the black cat. However, most people are concerned with the appearance of the cat.

You can read more about black cats and superstition on this page.