EV and IV training is more for the trainers who want to customize and design their own unique team. Some do it, others dont. It entirley depends on what you want out of the game, because besides, once you've completed the game and maybe obtained all the Pokemon, what else is there left to do? It can increase the longivity of the game and give it a purpose after the story.
I'm in the process of desiging my own Ev trained team, but it is my first attempt so its taking me a while. I'm hoping to EV train my favorites, that way at least I know they are the strongest I can make them and if I lose in battle itll be down to my choices. But it will feel great when I win my first battle with them ( if i ever do lol :P). Im not in it to be the best at battling, I'm not going to be a really competitive battler like that. I'm gonna battle for the sheer fun of it, while I secretly snigger at the sore winners I may come across ;)