Given that the windows in NSW unit blocks are normally common property, it will probably become the responsibility of the owners corporation to fit the locks. So that's extra funds that will be required, and that's assuming the owners corporation can get access to every unit that is affected. Then what has to be done to ensure the locks remain in place - annual inspections? That's more costs and more access issues, just like annual fire safety inspections.
I could comment ad nauseum on the lack of personal (let alone parental) responsibility that is expected of people these days, but I'm sure most people here feel the same way. Anyway, I'm just a greedy landlord so I suppose I should just cough up and shut up.