It seems like everywhere I look these days there is somebody spewing out some nonsense about how nobody will do anything in a game if it is not allotted a sufficient "reward", where reward is some shiny trinket that your character can keep.
In one form or another, the human race has been playing games for thousands of years. Despite the astronomical salaries attached to some pro sports stars, most people are perfectly content to play games completely for the fun of the game itself. When you checkmate the king in chess you don't look around expectantly waiting for his treasure chest to materialize in front of you, you set up another game and set to thinking about how you're going to take down your opponent this time.
This new bribery of sorts is a thing pertaining specifically to MMO's. Single player RPG's rewarded people with trinkets all the time, but it never became an issue because the games didn't involve "grind". Everything you did was moving you closer towards completion of the story, and very few encounters were the same as any others. Therefore you actually enjoyed what you were doing, and so did not need to be "motivated" to play through the game.
Most MMO's, on the other hand, are painful. Everything you do is the same as everything else you've already done, and so players actually have to be goaded, much like cattle, into going down a particular path.
The worst part is, there are some people who seem to accept this as par for the course, and play games only if the progression of juicy "rewards" fits their expectations.
These people are what are referred to, in general, as "Loot Whores". Don't get me wrong, we all love loot to a certain degree, but most of us can appreciate the fun or lack-thereof of the gameplay in some way or another. But the loot whore is a beast who has eschewed all forms of gameplay in favor of pure, pathological desire to obtain more loot.
Loot Whores come in two distinct flavours. The first is probably the most obnoxious, because they pretend to be "hardcore" in their appreciation for particular elements of gameplay. In actual fact, all species of Loot Whore care only about loot, but these "hardcore" beasts require their loot in a given context. Some players require that the loot only be acquired in the presence of at least 20 other people, or perhaps that the loot is not able to be obtained by at least 90% of the other people playing the game. The most obnoxious kind require the loot to be taken from other players.
The less "hardcore" flavour of loot whore is less bothersome, in that they will take their loot however they can get it. However, make no mistake - they are still a parasite on the soul of the video game industry, swaying the game developers towards removing all vestiges of gameplay from their games until all we're left with are glorified slot machines with a chat window.
What can you say to the Loot Whore to lead them back to the path of the righteous? I suspect that there is precious little, it is probably already too late for most. Perhaps the direct approach is the best. Sit them down, look them in the eye, and ask to them to please explain why they would give two shits about whatever they're complaining about if the game wasn't an MMO.