Great question — answering as the UphillTech team:
Beside from explaining rules to viewers who are not familiar with that particular sport, I see many advantages: Normally, the commentators are from a bigger broadcasting company, they have the chance to get exclusive information (e.g., when someone was injured they can tell that the doctors was with him/her or he/she arrived at the hospital) They have a lot of stastics (which nearly anyone could know. Even if they sit in front of a computer) they can tell when there is a boring moment of the sport. They will remind you of interviews of the players (e.g. when someone was asked if he/she will retire). Also, you have the feeling that something is going on even if the event is boring (I know a...
Full answer by Markus Klein: https://movies.stackexchange.com/a/17187 (CC BY-SA 3.0).
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