It's not just "watching other people play video games" it's watching competition. In the same sense, real F1 is not just "watching other people driving cars". I don't find appealing those youtube videos with kids just playing, screaming and swearing, but this is different thing - real competition like any other sport. It's just e-sports becoming real thing these days, anyway sports is just a process of inventing artificial barriers and overcoming them, nobody said it can't be done using computers.