An odd question perhaps, but why do so many homes not have locks on their bathroom and toilet doors?

An odd question perhaps, but why do so many homes not have locks on their bathroom and toilet doors?
Maybe this is just something that's unique to Australia, but I've been in so many houses and so many of them didn't have locks on either the toilet or bathroom doors. The house that I'm living in now (my sister's house) was built during the 1930's, and the doors didn't have locks. The house that I lived in prior didn't have locks either, and we had to install them.
An odd question perhaps, but why do so many homes not have locks on their bathroom and toilet doors?
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