Because this is ridiculous.

Australia's government is "banning" adult publications and films featuring women with "small breasts," says Aussie activist Fiona Patten, on the grounds that such images encourage pedophilia. Patton, leader of the anti-censorship Australian Sex Party, is taking issue with a 2005 ruling which specified that even depictions of women who are over 18 but "appear to be" underage may be judged "illegal." Is this alleged practice a strategic way to fight child pornography, or — as Patten maintains — an absurd reaction to a perfectly normal female body type?

How could censoring small breasts curb kiddie porn? This "is a terrible idea for many reasons," says Maureen O'Connor in Gawker. Not only would such a ban do nothing to "reduce smut," censoring images of "small breasts" only codifies "an arbitrary set of female sexual ideals."

"Prude Australians try to ban small boobs and female ejaculation in porn"

Patton is exaggerating: We're all taking this too far, says Australian censorship blog Somebody Think of the Children. While it's true that the law does ban women who "look younger" than 18 from appearing in adult publications and films, images of small breasts alone are not "automatically" considered "illegal." For instance, "it’s highly unlikely that a naked photograph of a 30-, 40- or 50-year-old woman with small breasts" would ever be banned.

"Australia bans small breasts"

Regardless, the law is sexist: A ban that classifies normal female bodies as "obscene" could not be "any more insulting," says adult industry blog Ms Naughty. Not only does this encourage women to have breast augmentations, it characterizes men who think "small boobs are sexy" as "perverts." There's an easier way to determine if a woman is "'too young" — it's called checking her date of birth.

"Now Australia is banning small boobs".

Source: http://www.theweek.com/article/index/105766/Australias_small_breast_ban