Well, let's see. There's the sense of accomplishment. There's the energy of the spectators. There's the fun of themed races like the WDW Marathon. There's the pursuit of a new personal record. There's the motivation to maintain my physical fitness.
Is that why I run marathons?
No. I run marathons because the week after the marathon, I DON'T HAVE TO RUN AT ALL.
I can totally justify taking a full week off. And that week, guys, that week is the BEST. The sleeping in. The hanging out. The complete lack of guilt while you do it. It makes the whole training cycle worth it.
So if you're on the fence about signing up for your first marathon, I say DO IT. Because otherwise, you'll never know the sweet, sweet bliss of being done.