It took me ages to realize that most people NEVER ask why. They don't look outside their sphere of existence and wonder what's going on in everyone else's life. In fact, they might argue that asking why is pretty much like being nosy about things that aren't your business. But that isn't how I see it. Being nosy would be obsessing over their particular situation and taking steps to find out who they were and what was happening with them.
Nope, why is just a catalyst. Asking why makes your brain creak into action and start putting together possible scenarios. You begin to come up with ideas. And those ideas spawn other ideas, and THAT is how creativity sparks and stories are fabricated.
So next time you sit at a stoplight, look around and see what's going on. You never know which car might hold the creative spark that'll explode into the next novel you read.