I think the problem for these people is, that they are only able to measure success by numbers.
They don´t see an abstract way of "playing", levels are a way measure what they've accomplished in a certain amount of time. The less time, the better.
And when they´ve reached the end of that line they´re stuck without the feeling of accomplishment and success.
Of course its an extremely limited way of looking at a game. And by looking at a game this way, they´re limiting themselves. And in the course of things, the gameplay of others, by forcing their "boredom" on them.
If these folks could somehow be convinced of these facts and that "numbers aren´t everything", they might even find new enjoyment in the games they´re playing.
But alas, many of these folks either don´t want to learn or don´t care about what others think.
Of course they do have a right to their own "style of play" and nobody would argue against it here I think, but hopefully they might some day be convinced that by just going through the motions time and again in any game they play, they´re actually harming the industry.
By putting unneeded pressure on the Devs, who are then forced to do half assed jobs in the time frame they´re given and churn out more and more of the usual grind routine games, just to keep the money flowing. Which in turn causes the players to complain about said jobs and the repetitive nature of MMOs in general.
Its a very sad fact, and a conundrum that is not easily solved.
CU
Acridiel