The New York Times reports that several studios have, like Disney, adopted policies that discourage smoking in movies marketed to minors:
Under pressure from an antismoking lobby unsatisfied by a promise that the industry's trade group made in May to consider tobacco use as a factor in film ratings, the six largest studio owners have been patching together individual responses to those who want cigarettes out of films rated G, PG or PG-13.
Smoking opponents view the result as surprising progress toward a virtual ban on tobacco images in all but films with R or NC-17 ratings.
The Times notes that 20th Century Fox started cracking down on smoking scenes in 2004 but "has been reluctant to make a public issue of the studio's policy, for fear that it might open the door to demands from groups with other causes, or put the studio at a competitive disadvantage with filmmakers who see blanket restrictions on smoking as threatening the credibility of their work." One such filmmaker, Dreamgirls writer/director Bill Condon, tells the Times:
It's a chilling idea. Movies are supposed to reflect reality. You're taking away a detail that is one of the more defining aspects of a lifestyle.
As for "demands from groups with other causes," the possibilities seem endless. Under the "not in front of the kids" rationale for smoke-free movies, any depiction of any behavior that might lead to disease or injury, including speeding, gunplay, gluttony, and sloth (not to mention morally controversial practices such as fishing, meat eating, fur wearing, and SUV driving) is fair game. It's not hard to see why Fox has refrained from bragging about its anti-tobacco policy.
I commented on Disney's cinematic smoking policy in the Los Angeles Times last summer.