Or maybe it's like any other competitive sport, there are people who enjoy watching it being played at a higher level than they themselves are able to participate at?
I feel like this with League of Legends. The top players streaming is a completely different game than when I play. The strategies are very different and the games have a more natural flow to them. When I play as a "baddie" the games are often just a lot of discord.
Beyond that, there are players who don't like each other and sometimes they end up on the same team. It probably wouldn't work if the players were all anonymous and I didn't know who I was watching. Beyond the soap opera and the drama it's a good way to learn and see my deficiencies so then when I do play I have a point of reference to base my play against in an attempt to improve.