To me, as if my opinion mattered, it seems that achievements are a "false" reward for doing something that amounts to nothing. That is, like some lab animal, if you jump through the hoop, you get the meaningless cheese puff. The difference being that lab animals are smart enough not to pay for their "achievements". And when I say meaningless, I am implying that, to me, curing cancer is an achievement, but killing some video game boss with 8 other people amounts to, sadly, nothing.
I am a gamer, hardcore, my entire life. I own every video game system ever made, and I do enjoy gaming. But, I fully believe that achievements on any game NEVER define a gamer, or how good you are at anything in games (especially MMO's). And the only achievements that matter in the world are ones that effect other people in positive ways in the REAL world. That said, if your self esteem is low or you compulsively/habitually need a reward of some kind to feel a shred of accomplishment, then I respect your decision, but I also pity you at the same time. Game on!