It occurred to me that one reason why having an announcer is useful when watching a competitive sport being played is because it reduces how much you need to know and think in order to understand what is going on. Announcers describe things like the histories of particular players, the roles of people in each position, and strategies. This lets you enjoy the spectacle without remembering everything about it, and without having to exert excessive effort to understanding what is going on. That is particularly useful in complicated sports with lots of rules, like baseball and football. Sports obsessives may find it surprising, but I think ordinary people tire of remembering a million complicated rules (just as ordinary people probably tire of the numerous and often arbitrary rules of grammar adored by pedants).
It also occurred to me that there are sports that forego announcers, often at least partly because they clash with the sport’s aesthetic. Dancers, figure skaters, and ballet dancers are expected to be silent and make it look easy. Having announcers overlaid on top of them seems crass, and like it would detract from the art.
It could be an interesting performance piece, however, to overlay constant narration onto an athletic performance that usually lacks it. A ballet with hockey-style announcers might be more accessible to people who don’t know much about ballet and who don’t want to spend the whole show puzzling about what is going on (the same reason there are short summaries at the start of Shakespeare’s plays – perhaps modern novels should have those too).