A player broadcasting his view has value of its own. In League of Legends, we don't see the player's perspective in spectator mode. We don't see what they type

A player broadcasting his view has value of its own. In League of Legends, we don't see the player's perspective in spectator mode. We don't see what they type in team chat. We don't hear what they're saying. A dedicated client has its benefits as well for the same reasons. You can change the view and look at things from different perspectives or look at places that the streamer (who is not necessarily the player I guess) is not looking at.