A group of mostly anonymous people vote for what movies they like. I can't imagine why this should interest me, or anyone, in the slightest. I can look at user ratings at the IMDb, I can read user reviews there or at Amazon, I can read critics' opinions on dozens and dozens of websites, or look at the critical consensus on Rotten Tomatoes. Yet some group of somebodies gives their opinion, and it's a big deal.
Well, on certain specific awards, it's a little more interesting than that, since they're voted by people in the field. For instance, visual effects technicians vote on the visual effects awards. That's why Button won over far more epically spectacular effects movies. The guys who make the effects know it is more difficult and impressive to make a CG person completely believable for large chunks of film time, especially in closeups (as Benjamin Button for a very large chunk of its runtime) than it is to make, say, a robotic suit flying look believable. That's just the way it is. It's why The Two Towers was a shoe-in for Visual Effects - not for its massive CG battles and world creation, but more particularly for a fully CG character who was still completely believable on a human (sort of) level.