This is really a difficult topic, in one hand you have the anti scouting arguments which are really valid. But in the other hand try to look at it from a spectator perspective.
If I, for some reason, were to start spectating a tournament in the final rounds, and I see a match with a player I know vs an unknown player, I would like to check out a previous match of the opponent, be it for 10min at least. Just for background curiosity.
Other one, if I'm spectating from the beginning, I tend to select the matches with the best players because those tend to be entertaining. But just as you are paying attention to a branch of the tourney a literallywho shrekts the other branch. And now this player is facing frags on the final. You surely will find yourself surprised and will want to spectate this unknown player previous matches to know what kind of sorcery he is using.
These are lame examples at best, if you will. But having all the information available as the tournament unfolds enables all these small things that make the system enjoyable, It's all down to user friendliness as DS pointed out previously.