Can I join in the fun?
The main reason we don't do litres over here is because we're American, doggone it, and standardized measures just aren't in our nature. We have a mile rather than a Kilometer, yards rather than meters, and gallons rather than litres. Because miles, yards, and gallons are complex, and we like our complicated systems!
(Plus we fear change.... do you have any idea how much the mileage signs on the road scare me?
Knoxville 19mi
Knoxville 12km
On the SAME SIGN.... yie.... I need my teddy bear....)