unassisted triple play isn't really skill related though. It's a mixture of timing, positioning of players, reaction of runners, etc. Everything has to come together at the right time, more of a fluke.
ALL of these things require a fair amount of random chance (aka luck) though. If a pitcher had the pure skill to get 20Ks in a game, it would happen more often. Don't under estimate how much random chance plays in sports. In half a million baseball games, you should expect a least a few perfect games/20K games/4HR games just due to random chance. How many HOF guys never had a perfect game or hit 4 HR? How many of the guys that did have incredible games aren't in the HOF?