I find stories to only be important for unconventional RP. Otherwise, there isn't much reason to have one unless you enjoy writing them. I mean, if you're flying around with your cap (at least give it an RP name?), most people aren't going to PM you and ask if you have a story for it. If you RP it well, people might ask out of curiosity (maybe the want to read it or something), and if you don't RP it, they just call you a capwhore.
I personally lack the time, patience, and creativity to write stories.