Most people are considerate--some are NOT--they are winning! If a stadium full of people should dare to object, there will be a 747 full of child advocates flying in from DC, forming an impromptu flash mob protesting, throwing organic baby food and soiled diapers at the sponsors, with a full contingent of media cameras showing it live on CNN breaking news. There are people who even bring infants to the courts, letting them cry the entire time while they have fun playing tennis--that's mainly on the left coast.
"...the human emotional system was not designed to endure the mental rigors of a tennis match." Dr. Allen Fox