Well I've heard stories about people needing them before. When I worked at The
Disney Store, a guest was buying tickets and was tellnig me that on their previous trip, they had been asked for proof of age since their child looked older than 3. They had to call a friend who worked at the hospital their child was born in and she had to quickly fax over the birth certificate. It was a hassle for her. For the most part, people haven't been asked, but I guess it's always better to play it safe just in case.