Left turns are hard
Tougher to make
Crossing lanes of traffic
Many chances to take

Left speaks to the idea of taking the harder choice. In driving, to turn left means to cross into the path of oncoming traffic. To turn right means easily merging into the flow of traffic. Statistically left turns are a lot more dangerous which means if you color that idea with the idea of making choices, the harder of the two choices is akin to a left turn.