Why do all children's cereal mascots seem to be male?

Probably because when the cereals were being introduced in the 60's, 70's and 80's their ad/marketing guys were men, and after 20 or 30 years of putting money into a brand image they're not willing to change the mascot. Might be a good opportunity for a cereal company to introduce Bizzy Suzie Cereal grab the other 51% of children that aren't boys.