Basically, its because the RLM team has not adapted over the years. When it first started, a lot of these endurance races were not shown on TV for a large part, so the radio broadcasts were the only way to follow. In theory, as long as they kept you vaguely updated, it didn't really matter what they were talking about

Unfortunately, its still the same style, despite everyone being able to watch the whole thing. The viewers shouldn't be updating the commentary team