Why is the Spitball illegal?

Why is the Spitball illegal? The reason why the spitball was banned was that it was regarded as doctoring a baseball. And everything that was considered doctoring a baseball was banned on this day in 1920. Throwing the spitball before that 10th of February 1920 was a common thing. Many pitchers did it.

The reason why the spitball was banned was that it was regarded as doctoring a baseball. And everything that was considered doctoring a baseball was banned on this day in 1920. Throwing the spitball before that 10th of February 1920 was a common thing. Many pitchers did it.