In some countries people drive on the left side of the road. This strange quirk perplexes the rest of the world; but there is a perfectly good reason.
In the past, almost everybody travelled on the left side of the road because that was the most sensible option for feudal, violent societies. Since most people are right-handed, swordsmen preferred to keep to the left in order to have their right arm nearer to an opponent and their scabbard further from him. Moreover, it reduced the chance of the scabbard hitting other people.