They don't even do that though. A pitcher doesn't really control his ERA very much, the other teams offense controls 50% and the pitchers fielders control a portion, the relievers control part of it and of course a portion is always just dumb luck, that is why an elite pitcher is only 1-1.5 runs a game better than a merely average pitcher, they just can't control a lot of it. Baseball is still a team sport and most stats are individual stats, they can't really tell you how valuable a player was to the team, they are just results of how the team ended up doing in certain situations. To me it seems you are a very results oriented thinker so I doubt we are going to see eye to eye on things. It is a team sport, the results aren't generally in control of an individual. It takes a long time for the results in baseball to have any meaning at all. A pitcher can be pitching great and give up a bunch of ER and the result I take from that is he is pitching great. You can be walking a ton of guys, not striking anyone out and getting lucky all over and not giving up many runs and the result of that is you are pitching poorly. The only way to cut out all the noise is to have such a large foundation of evidence that you can spot clear trends and for ERA or defensive stats that takes more than a year worth of data.