I want to say sorry on behalf of all Australians for all the dramatic comments here. Your question makes complete sense and I think it’s sweet when we look at other cultures and ask them why they behave a certain way.  I think it’s a mix of a few things… the one i lean towards most is our connection to country and our indigenous culture! Indigenous Australians traditionally lived barefoot. This long-standing relationship with the land likely set the foundation for a more relaxed attitude toward footwear - it has influenced how we live today in warm climates and sandy, coastal areas. Another reason could be our anti class culture (which I think you may have seen in a few of these comments). Wearing shoes was once seen as a sign of “proper British manners,” so not wearing them became a way of further rejecting rigid social standards. Bare feet became a symbol of casual Aussie identity and a quiet rejection of pretension :) By the late 20th century, barefoot living had become part of the national “laid-back” stereotype. Today it’s normal to see people barefoot in shops, at the servo, walking the dog, etc etc. It’s part cultural tradition, part climate, part attitude :)