Not sure why.
Gaylord Perry even wrote a how-to book on throwing spitballs, published while he was still playing! Perry was later voted into the hall of Fame.
WikipediaMe and the Spitter: An Autobiographical Confession is a 1974 autobiography by Major League Baseball (MLB) pitcher Gaylord Perry, written with Bob Sudyk, a sportswriter for the Cleveland Press. The book details how Perry cheated at baseball by doctoring the ball. The book covers Perry's early life in...
https://en.wikipedia.org/wiki/Me_and_the_Spitter