Same reason people watch video game players play games. Seeing exactly how experts do things, in real situations, can be valuable if you're trying to attain your own mastery. And entertaining if not.
Some people watch football, golf, or billiards. Some people watch poker or chess tournaments. Some people like to watch carpenters work or houses be remodeled.
I like to watch other people code. I assume that somewhere in the world there's other people like me.
I like to watch other people code. I assume that somewhere in the world there's other people like me.