If you have been to Disneyland have you ever noticed little children running around in costumes?
Disney really loves it when kids wear costumes of their favorite characters to the park and/or you can even purchase a makeover for your kids at the park! Apparently once your child is 14, you are no longer allowed to wear costumes to Disney Parks! Ahhhh!
This is why, It's in the parks official rule-book! Guests will be refused to enter the park if they are wearing costumes and masks. There are exceptions for certain occasions but the rules are the rules, the employees too have to obey the dress code.