The big dept stores don't like it - it's a big business thing, and Myer has had this rule for a while - there used to be signs, but not enough and in small print. It's more about stock loss and people mapping a way to get stock out. Well, it was in my day, before phones had cameras and before everyone had mobiles, so I suspect it's even more about that than ever before.
I don't shop there when I'm not an employee, and I actively avoid shopping centres, so taking photos where I shop now isn't an issue