The Wrong Side

I learned today that drivers in India drive on the left side of the road like in England.  I guess that makes some sense because India was part of the English empire for a long time.  And I was told that all of Asia, with a couple of exceptions, also drives on the left side.  I was surprised to learn those facts.

I've heard that the British drive on the left because of history.  In the chariot days the drivers drove on the left so they could slash the other guy with the sword in their right hand, being right handed.  At least that's what I've heard.  I've been in Austria, Germany and Poland.  They drive on the right side and had a horse & sword time period.  Why don't they drive on the left?