First of all, everyone is going to be playing the game themselves for quite some time. Why watch someone else play when you could play it yourself and discover new things?
Second, most people are going to want to avoid spoilers until they find it themselves in the game.
Third, It's probably not going to be that fun to watch people learn how to play the game. Most people are pretty awkward with a game's controls and gameplay when they first get it. Why would we want to watch someone else struggle to get the hang of things, except maybe for a laugh? I think people would much rather watch a playthrough from an experienced veteran of the game, showing how impressive they are and showing the viewers the best ways to get past particularly difficult parts.