There are a few reasons I can think of to explain why people may do stuff like that without going off roading:
1) Aesthetics. Some people just like the look of customized accessories. Maybe they don't use it for what it is fully capable of, but we have all bought stuff for no other reason that it looks cool. A steel bumper will protect you against a shopping cart as well as a giant rock.
2) Hobbyists and forever modders. I almost fall in this group. I picked up offroading because as a mechanical engineer, I love tinkering with things. My last vehicle was a BMW 318ti...lowered to the ground, nice suspension, fun zippy little car. I barely ever auto cross raced it despite all the mods I did to it. I liked excuses to modify and change things more than I did actually racing it. I got my Xterra simply because I needed something to navigate through the snow. As an Xtension of my tinker-filled-mechanical mind, I started modding it. I got into offroading simply because I liked working on the truck. I first lifted it and modified it without any interest in off roading.
3) Being different. There are a ton of Xterras with 3" SL 2" BL Shrocks all around. Never seen one similar to this. Some people just like the challenge of thinking outside the box and creating something original. Might not make sense to you or me...but hey...it doesn't have to