Why is it seemingly forbidden for a lefty to play catcher?
Lefties would have an advantage fielding bunts and throwing to first, as they would already be oriented towards first when getting the ball.
When throwing to second, it seems meaningless which hand to throw from.
Throwing to third would require you to turn around, but I believe that throwing to first, either on a dropped third, bunt, or pickoff attempt is more common than throwing to third.
Is there something I'm missing?
Well, there are a few downsides for left handed catchers, such as throwing out a base stealer at 3B, which would probably happen more often with a left handed catcher, but probably the biggest reason is pointed out in this quote I found in this ESPN.com article:
Distefano offered two explanations. Bunts toward third base, he said, cause problems for left-handed catchers. In scampering to grab the ball, transferring it to their left hand and throwing to either first or second base, their bodies get closed and clumsy. Throws for right-handers are far more open and natural. But the primary problem Distefano encountered was with plays at home. Because his glove was on his right hand, every accurate throw to the runner's side of the plate would have to be reached for backhanded, impeding a quick tag. And on outfielder throws up the first-base line, reaching out with his right hand would leave his throwing shoulder wide open to the runner.
"If there's going to be a bang-bang play, the left-handed catcher's going to get hurt,” he said.
The most frequent throw a catcher makes (besides throwing the ball back to the pitcher) is to throw out a runner on first base trying to steal second base. Because it is the most frequent throw, and because it keeps the runner from advancing to a scoring position (runner can score from 2nd base on a single), it is also the most consequential throw a catcher makes. A large majority of baseball players are right handed and bat right handed. That means, the majority of time, there is a right handed batter in the batters box. A right handed batter is in the way of the throw to second base from a left handed catcher. As second based is the farthest base to the catcher every split second counts. Any impedance to the throw and avoidance of the batter can make the difference between an out or a person in scoring position.
The tag plays at the plate would become more difficult and the LH catchers can not put swipe tags down. They have to turn their body to tag instead of having the ball travel to the tag.
I think it can be argued for or against in any situation. I don’t believe that a bunt play is why there hasn’t been a leftie catcher in the last 20+ years. It would probably stem from the lack of young left handers and their youth coaches trying to utilize them in pitching roles or 1st base. Plus, not a lot of kids like playing catcher and if you’re a good youth left handed player, coaches won’t risk you getting beat up behind the plate.
