The Grind=Money is an intentional part of the MMO-Trap. What I call "the illusion of progress".
You grind to unlock bigger numbers. The first "half" (if can apply a mathematical limit to a game with no definitive "end") of the game is spent acquiring skills. This is essentially "training" and the only point in the game where you make actual progress.
After a certain point, the focus changes and you use said skills to start acquiring items not out of luxury, but necessity. You will repeat this process until you quit or the game server shuts down.
This is the interesting thing about MMOs: The game offers no definitive end.
A game without a real definitive end, (either through victory or loss) means no closure.
So instead of a game, it ultimately becomes a habit, and then possibly an addiction.
Before I continue, I am not just picking on World of Warcraft here. This model is true of every single MMO I have tried, including Ragnarok, Dofus, Runescape, Maple Story and others. The gimmick is different, but the model is the same.
Ultimately, there just isn't a whole lot to do in most MMOs. There are essentially 3 missions: "Go there." "Kill them." "Fetch these."
The gameplay never once evolves beyond its original premise in the slightest. That would not be so bad in in theory (the mark of a good game is one where you are required to master your skills), but it's uniquely problematic in a game where you are required to spend a tremendous amount of time to accomplish anything.
And then game asks you to do the same exact task, with the same exact skills in the same exact manner with your only reward being the ability to DO IT ALL AGAIN.
Thus, it's all an illusion that you are making progress, because you are not. You are counting to infinity, being "rewarded" with the privilege to keep doing so.
"Harder" simply means scaling the game up a bit. You will fight new models of enemies with bigger numbers.
To use the more recent example: Not a single fight in WoW ever became technically "harder" except for the artificial handicap that was equipment, which I could only solve through GRINDING MORE.
I never used my skills in new scenarios that made me think (with the sole exception of PvP, which is an entirely different issue). It was actually appalling that people were constantly cocking it up, because every single scenario can be beaten with a flowchart.
You might get fooled by a gimmick, but make one or two little adjustments, and you are left with a game that has a huge void of pointless grind punctuated with moments of creativity; Just enough morsels to keep the average player fooled into continuing.
After I finished my 2 week trial of WoW (I saved the "best" for last during my little MMO study) convinced that there are two major reasons why anyone would subject themselves to this for months at a time:
1) It's psychologically controlling. We instinctively respond positively to completing tasks it seems, and MMOs are full of easy tasks with deceptively hard (equipment or party requirement) prerequisites. Working towards an item or finishing a dungeon is rewarding to say the least. If the game had closure, this might have meaning. However, since your successes are temporary at best, the process goes on.
It certainly was not because the game itself was consistently fun. I listened to Ventrilo channels and chat logs, and most of the people seemed to be mentally exhausted or bored, only becoming excited when they finished grinding for their latest shiny, then relapsing into relative lethargy.
It's a fact that the amount of time spent grinding ensures that this trend is the norm, not the exception. Remember: the game company makes continuous profits off of you by deliberately wasting your time.
2) Social connections. Friends can make damn near anything better (or to be accurate, more bearable). Enough said.