After slaying a lowly monster in your favorite MMORPG you expect it to drop a small amount of coin, a basic food item, or some other fairly predictable object that likely has little worth to you directly. Once in awhile you'll find something more valuable, but it may take time. As you walk around and fight monsters this can become extremely repetitive and boring. What if you were able to obtain items in a "casino" style fashion, similar to the Diablo series but built for MMORPGs?
Ultima Online, one of my favorite MMORPGs, was all about item generation, economics through trading of those items, and the community that helped guide which items were popular or useful. EverQuest, Dark Age of Camelot and Star Wars Galaxies have employed similar item systems. They do not target items as the main theme of the game like Ultima Online does, however, they still use items as there core economic engines. Especially Ultima Online, these games require the user to obtain items and property in such a way that it ultimately becomes redundant and down right boring.
Is predictable item statistic generation necessarily a bad system? Not at all. For example, when you are participating in a quest or are after a particular weapon, you would like to be certain that the creature you are spending time fighting will eventually drop the item. You might ask yourself, "Is this not random item generation?" If it isn't, then wouldn't the item in question come up every single time, or not at all? Item generation in all games is "random" to a certain extent.
What games need that employ any sort of serious item based system is a more Diablo style random item generation technique. It is this "lottery" system that users will become excited in using, at least longer than traditional systems. The second benefit in such a system is the acceptance of a smaller pool of overall items. With a random item generation system players may be willing to ignore this limitation for slight tweaks and unique qualities of current items.
Let's take this one step further and add in the idea of random location spawns, and forget for a moment about the typical "kill a monster and a chest or bag appears". Replace this with simply a chest or a bag! For example, your character is strolling through the woods and happens upon a randomly generated chest. To open this chest you may have to go through a series of monster spawn battles or some other challenge, but once open any number of things may occur or spawn. A scroll to some great quest, an item that will help you on your journey, or a bit of coin.
As we can see there are many options for perking the player's interests without having to spend a huge amount of resources on developing overly complex systems that may not ever be used, or worse, rejected outright by the community as useless and boring to overall gameplay.