The main reason to get shiny pokemon is because when you've played the game loads, you want to set your own objectives, like catch a male/female of every pokemon/fill your PC with shiny pokemon. Pokemon is very much a sandbox game, do what you want to do to have fun. Playing it linear gets boring
Yeah, I agree with Torian, I mean I love it, but you have to do something extra in your game to really have fun. That's why I love the new pokewalker, my friend was using it yesterday when he was over my house and his staryu was gaining a lot of experience. Pretty sick.