Loss of intellect is generally used as a form of contrapasso–the punishment befitting the crime of the individual within a revenge story. So, generally, people like it because it’s a way to punish a character for wrong doing, like making a businessman who crashed the stock market through clever derivatives, unable to do the simplest math problem. The loss of intellect generally isn’t erotic–but it works as a specific trigger within what I would call the “revenge genre.”
That said, I know some people who do like the idea of losing intelligence as a positive thing. It’s not nearly as common, but for them the idea losing some cognitive ability is all about being able to live a simpler life. They might feel too smart in their day to day life, pressured to succeed because of their intellect, and the idea of being a simple minded jock or redneck who just sits around and masturbates all day turns them on, because it would be a easier life. It doesn’t work for everyone, but that’s the basic impetus.
Bracken's Corner 