There's a large percentage of Australians, it seems, who fall into the category of "apatheist" - those who just don't care about religion, even though they nominally consider themselves a member of a religion.
Consider this: In the 2006 Census, 18.7% of people in Australia stated they had no religion. However,
the Australian Bureau of Statistics' 2008 Year Book had this to say:
According to the household survey, conducted by the ABS during the period March to July 2006, 20% of adults participated in religious or spiritual groups or organisations during the 12 months prior to interview. Among 18-24 year olds, 21% of women and 14% of men had participated in religious or spiritual groups or organisations. Rates for people 65 years and over were higher at 25% for women and 23% for men. While participation for this age group is similar for both men and women, in general women (23%) were more likely than men (16%) to have participated in religious or spiritual groups or organisations. People born overseas (25%) were more likely than those born in Australia (18%) to have participated in religious or spiritual groups or organisations.
So, even though 69.5% of people specified a religion (and 11.9% failed to fill in the question sufficiently to be categorised), only 20% actually participated in their religion. I really do think that the message "it's okay to call yourself an atheist" is one that can really be effective in Australia. I don't think I'm the best at getting that message across, but I try.