After Mock's comment, I've been trying to watch Jorge Posada more critically. I don't know. I have a natural sympathy for catchers. It is, without a doubt, one of the most thankless positions in sports. I can't help but admire someone who's done it so well for so long, particularly when they also manage to make offensive contributions along the way. You can't hide a bat at catcher. You can't really hide one at shortstop, second base or center field either but the fielding demands on a catcher go far beyond those of other every day players. How anyone handles a major league pitching staff without an advanced degree in psychology is astonishing to me.
Every sport has these disparities to varying degrees. In football, I'd say it's offensive guards who get the short end. In soccer, it's defensemen with even goalkeepers getting a bit more glory. Hockey does reasonably well. The plus/minus rating is a wonderful statistic which helps to showcase the contributions of defensemen. Penalty minutes are also badges of honor for the league's enforcers. Even so, a high-scoring forward is more likely to win an MVP trophy. Basketball seems to offer five equal positions but a closer look at history shows that a weakness at center or point guard is a far greater liability than deficiencies at the other three spots.
I highly recommend Roger Angell's Season Ticket. His chapter on catchers is a must read.