The only reason that they do this is to prevent scratching up or marring the wheel. It's like a fine piece of furniture. It also helps prevent injury. Not all casinos have the rule. The casino also doesn't want a wheel to have identifiable marks or scratches on the frets since many new wheels have indexable pocket compartments/number tapes. Regarding most dealers being right handed. The percentages are pretty much the same as they are in the general population. Spinning a roulette ball is very easy. Most dealers can spin with either hand. In AC every live wheel is right handed, but that doesn't mean that every dealer is by any means right handed. Across the rest of the country left handed tables are far more common. Most of the time though there are more right handed wheels than left handed wheels. It really depends on where the casino wants to put the game within the casino as to whether or not the game is left or right handed.