Females tend to be easier to sell since males can breed multiple females. Even though it’s not advisable, females can also be housed together while males can never be housed together and should be separated from females when not breeding.
Also, folks that are working with super high quality or special characteristics sometimes want to keep their cool stuff special and limit the males they release to limit the number of offspring that can be produced in a single year. For example, I believe I remember that Ron Tremper didn’t let males go for the first couple years that his albino strain was on the market. That kept his prices super high since it took others a minimum of two breeding seasons to produce albinos.