If they had resorted to instant replay after that call, that game would have gone on FOREVER. But seriously. There's nothing wrong with getting a play right and ensuring the right outcome, but no single play can ever carry the weight that single plays in the other of the Big 4 Sports can carry. There's no clock or sudden death, and there are ~4374 outs per season. And as hard as it is to believe, umps get nearly every call right. It's true that the Pirates could very well finish up the season one game out of first and look back on that one play. It's also true that this blown call was the difference between the Pirates losing in 19 and the Pirates losing in 33. They also had 18 innings' worth of opportunities to put an extra run on the board. Also, if they end up a game out of first at the end of the season, there will be this singular what-if among 75-ish other losses for which the blame will fall on simply having a game inferior to their opponent. It's not about the human element, and it's not about keeping a slow game from getting slower, it's about practicality. There are several plays every single game which are replay-worthy that don't amount to anything. There would literally be tens (hundreds?) of thousands of regular-season replays before you could ever definitively point to one call reversal/confirmation that ended up having a significant impact on the end-of-season standings. I'm not at all opposed to replay, I just think its current lack of implementation is plenty understandable.