The only being an island is does, it is makes it easier to not have to deal with crazy things like a road where everyone has to swap around at the border.Why would we want to drive on the right, like those backward Imperial-using Americans? Surely the only reason to adopt such a practice is so you can fire guns from wholly inside the car, or simply to be childish and stick it to the Brits from whom you just declared independence?
Most people are right-side dominant - Driving on the left allows the dominant eye to focus on oncoming traffic & keeps the dominant hand on the steering wheel, even when shifting in a car with a manual gearbox. Also, I believe all motorcycles are set up for right-handers, for this very reason of dominant side handling the fine motor controls.
England, Scotland, Australia, Japan, Ireland, Hong Kong, Jamaica, New Zealand, Nepal, Barbados... most of the cool places drive on the left.
It does seem there's a lot of island nations that follow this, though. Maybe that's another factor?
Left/right drive is mostly a matter of choice and 90% of the world chose the other side.
Metric / imperial is a choice of backwards or forward. A few places have chosen backward!