Fads come and go but the desire to push one's body and potential to the very limit for competition is as old as mankind. Children naturally race and wrestle in all cultures and throughout all of history. Not everyone has the heart of an athlete but those who do span all levels of sport. I believe that there is enough of those that there will always be races.
I see a lot of people post on FB their intentions to participate in these type of things and then those who do post lots of pictures. None of these people become runners. They all want the rewards of being a runner but none of them really want to run. These events give them an entertaining shortcut to give them the reward of finishing a race and being able to get a FB pat on the back for being a runner. Of course I do admit that there is nothing wrong people doing this sort of thing for fun. I like to do things just for fun. Just don't expect me to think that you really accomplished any great fitness goal.
I really think that anyone that happens to start running while training for one of these things most likely would have anyway.
….says the woman in a Halloween Costume in a race where no one else is dressed up…..guess I need to go to Japan. They race fast and enjoy over the top spectacle.