It's a matter of where one obtains such things Kimi, it's not like that stuff can just be pulled out from the ground. Typically you have NPC's manufacture those things... But at a going rate of demand and availability. I.e. Freaking expensive. It's cheaper to level up then to purchase a good vehicle, which is why most are owned by max-leveled players or people who stole them. That and some events, such as the recent Dissolution attack, could end up [i]killing[/i] those NPC's, decreasing those who would have access to the correct people to make the stuff. 

Conventional harvesting of Deep Ground's natural materials is also nearly impossible: Only manufactured goods like buildings and such would remain after being "Destroyed". If you say, break apart a boulder, it'll eventually just vanish within the next few minutes. Certain structures would last longer or even survive the damage done, but anything that can't sustain itself just poofs. Dig a hole in the ground? Dirt's going to be gone. Chop down a tree? Wood, leafs, everything would vanish within a few minutes. It's why you'd get a lot of barren wastelands between the cities: Players have a habit of destroying the local nature, and unlike in the real world there's very little to make ti grow back. Aside from wasting precious EXP to restore nature.

Also understated, but Deep Ground IC does actually have a plot of sorts. Most people skip out on it for PvP, but there's [url=http://tvtropes.org/pmwiki/pmwiki.php/Main/StoryBreadcrumbs]bits and pieces[/url] scattered around. The fact that the plot isn't really in-your-face and you're more likely to get caught up in a Guild War makes Deep Ground's IC plot go unnoticed. And ultimately it doesn't really serve much of a function aside from giving context for why you're killing this Dissolution Boss and where it's at, something which easily be obtained from asking any sufficiently experienced player. 

Also that offering isn't enough. I want your loyalty. Your faith. Your dedication. And most of all, I want you to renounce your freedom and servitude to anyone else but [b]me[/b]. If you can't do that, then you aren't worthy.