When my parents helped me move cities a couple of months ago, I ended up navigating. It was dark for most of the journey, and instead of using the cab's roof light (which my Dad didn't want me to use because he was driving), I used my Photon II to see the map. A conversation followed on why I carry one, which resulted in my Mum asking for one for Christmas. She now carries a light on her keyring.

I reckon that if a person SEES how useful something is, they're more likely to carry it/use it/look after it.