Because the Americans (and nearly all others) are right. The English and Japanese are well, as you know...
Serious, 3 reasons...
1. The great majority of people are right handed
2. After the Revolution and before WW2, Americans often liked the French better than the the English.
3. Henry Ford.
A curiosity: Sweden switched from driving on the wrong side of the road to driving on the right side of the road. They did that - everywhere in that country - over a weekend. This back in the 1960's. I would have loved to been there on that weekend to witness that.... Perhaps someday the Brits will also realize what is right... and have a weekend like the Swedes did.
.
To change would be a pretty major issue.
Many junctions would work more or less normally if reversed but every single car on the road would be the wrong way around. If the driver sits in the middle of the road they can see further down the road. If the driver sits on the right and also drives on the right a lot of visibility would be lost.
You'd also need to reposition just about every single signpost, so it pointed the other way and/or was moved to the other side of the road. That alone would be a huge undertaking.
The Swedes did the right thing back in the '60's.... The Brits could too. @tango you are not suggesting that the Swedes are more able, more capable than the British are, are you?
IF they too had a weekend in which it all switched... well, I'd love to be there to witness that switch. I'll bet it would be a MESS. It was in Sweden.
@tango
I've always understood that the Brits have been okay with accepting the Right Way, the Wrong Way and the British Way.
.