Help me figure this out?

I dont understand why some people will run a big wide wheel on the rear of their pickups and flare the bedsides out!!!! i could understand like a 1/2" flare that would be unnoticible but a 2 1/2 come on thats a little far.. why not narrow the rear end?????????????

because it is a lot easier to flare a fender then it is to narrow a rear-end. oh and the cost may have something to do with is to