Because at times, lugging around a dSLR has become a liability especially if you're a shutterbug like me who always like to snap and capture priceless moments, wherever, whenever.
However, malls nowadays are restricting dSLR users to just shot pictures on their field without necessary permits. Malls, like Greenbelt for example, have guards trying to wane you whenever you pass by the garden(or any "shutterbuggable") area thinking that you'd take picture of the composite elements of the scenic surroundings. Weird is that these guards wouldn't mind you snapping a piece using your phone cam or your P&S.
So I either ended up bringing my iPhone 4 since it's the one I can just easily draw out from my pants. My P&S camera is neatly tucked inside my bag so I'm sure to miss a second whenever I need to shot something.
This is one of my iPhone photography takes. See how critical the moment is? A missed second would mean that the subject would have flown somewhere, or already beyond the reaches of my lens.