"I don't understand how you can continuously sit at a computer for multiple days without wanting to get up and do something else." More and more people are eager to play games, like World Of Warcraft. And they can play more than 12 hours a day with out interruption. Why is it so attractive?
That's because you and I have fully developed brains with an evolved sense of self awareness. People who die while playing video games tend to be very young, and the part of their brains which regulate things like impulse, decision making, and weighted analysis isn't fully developed. Also, videogames provide stimulating feedback for undestimulated young brains. Five years ago, I would sit in front of my computer and play Quake III Arena for twelve hours without getting hungry or thirsty. These days, my goal is to own everyone in about 45 minutes, because after that I'm going to do my studies, or go work on my car, or fix something around the house, or veg out in front of the news, or pay lipservice to my girlfriend.