It's not intrinsically better, it's just a convention, but it helps if everyone operates to the same standard for obvious reasons. Since neighbouring countries drove on the right, it was better to adopt the same standard. This was not an issue for islands such as the UK and Japan with no direct road links to neighbours, therefore they still drive on the left. Originally, before cars, the nobility rode their horses on the left to defend against oncoming traffic since they held their swords in their right hand. For that reason, peasants travelled on the right for safety. After the French Revolution it was prudent for the nobility to blend in, hence all traffic began to travel on the right which was then spread by the French empire.