If anyone understands ERA, and is vested in whatever league they are in, will usually know the number of innings a game is. Therefor the ERA, looking at the letters, is E-arned R-uns A-verage. So it just gives an idea, that if a pitcher were to pitch a complete game, (7 or 9 innings… or whatever the league you’re in) how many runs they would give up. It helps to give managers an idea of how much a team needs to score to overcome the deficit their pitcher will put them in on average.
