I would say it is because most people have learnt to get the back end out and keep it out on roundabouts, as they are the perfect thing to practice on ... Going the other way is a bit harder as your motor skills are not as tuned in to that direction as they are to the more dominant side, and also the LHD/ RHD thing is a factor, much easier to see the side from which you are driving to judge distances etc

Practice would sort it I am 99% sure