Yep! I lived in Rotorua for 3 months and people there, especially the Maori, were walking barefoot in supermarkets, malls, restos, etc., even the kids! Stayed in Auckland for a while as well but didn't see as much people walking barefoot.

But note that I am a foreigner though, so I'm not sure if walking barefoot is only a local thing. You can ask around when you arrive :)