It's because everyone is a frickin' hypocrite. If I cheat, it's gamesmanship, and I'm just doing what I have to do to keep up with everyone else. If you cheat, you are the scum that is destroying the integrity of the game.
Whenever you have millions of dollars on the line, individuals and teams are going to do anything they legally can, and anything illegal that they think they can get away with, to gain an advantage. In baseball, corking the bat, spitball/scuffball/foreign substances, and stealing signs are as old as the game.