The truth is most of the time in many (I suspect most places) if you go out and forget to lock the front door, you probably won't get burgled. I've done it often enough.

But being more aware of the possibility, and also knowing that, unlike most of our parents, there are probably a few things in our homes worth stealing, we sensibly enough prefer to lock up. However it's a real mistake to imagine that the picture of a threatening world ready to pounce on us if we ever let our guard up is true, even if it helps sell papers and padlocks.