I just can't get into that. It's a huge thing now. Some people don't even play games and just watch other people play games. In the first several decades, one of the worst things in gaming is watching other people play a game that you can't play. And now that's the big fad.
Something interesting is how flooded the gaming market is these days. There are so many good games out there, no adult could possibly have time or really the desire to want to sit at a computer/console all day playing them. So what I do enjoy about the online streaming is I can check the game out and determine if it really separates itself from other games in the flood or if it's just another FPS, RPG, etc with nothing new to offer.
I used to do it ALL the time during my lunch break at work. It began as simple as watching footage of StarCraft 2 or COD being played to improve my skills and satisfy my obsession with gaming. Then I'd watch gameplay footage of games I considered buying to see if it was worth my time to play.
Lately my obsession of video games has shifted to board games, and now I spend a great deal of free time and lunch breaks watching people play board games :P