Heels don't cheat as much. I suppose the reasoning is that in the 1960s, 1970s and 1980s it was not nearly as exposed. There weren't people who were or considered themselves to be "smart to the business." It was much more like a sporting event. Cheating in sporting events has been reviled for as long sports exist so it worked to get heat on a heel if he "cheated" during the match.
Now almost everybody knows it is a work so the cheating is not nearly to the extent to where it used to be when top heels were often the most innovative, ingenious and successful cheaters. THE DIRTIEST PLAYER IN THE GAME! WHOO!
I think it is a mistake. Letting heels cheat more and get wins by cheating would still get heat and make it so that the heels don't look like these total chumps who lose 70 percent of their matches, regardless of their experience and in-ring talent. 'Sup Ziggles.
Edit: Motherfucker, beaten to the punch by about half a minute. I got Pyro'd.