Even if the match or the event is exciting I could not watch it without these commentators they add value excitement and information to the matches they are the voice of the match or the events, even if you don't know much about the sports that you're watching you'll get insight and information by just listening to these commentators.
This is very true especially for audience who are relatively new/beginner on that type of sport/game.
I remember, in chess24, there are three (3) casters currently which are composed of two (2) grandmasters of the sport and one (1) caster that has little-to-no clue about chess. The good thing is, since chess is somehow a difficult sport to understand, these newbie watches can associate themselves with that lone beginner caster in order to understand fully the game. They can see the perspective and ask some questions that the lone caster would also ask these GMs in their field.
The benefit of having casters can definitely bring a lot on the table; not just pure commentary and entertainment but also some insightful knowledge about the game/sport itself.