If you can turn right, how come you can't turn left

Today on the ride home from Macey's grocery store, Ashton turned and whispered "Maya, Papa just turned right on a red light." I reassured him that it was okay when turning right at a red light. Then he asked "If you can turn right on a red, how come you have to wait to turn left" I laughed to myself and then said to him "Think about it, if you turn left you will most likely get hit by a car. If you turn right you're okay." "Oh," then he went back to making his airplane noises. I love this kid to death.
That's all for now.
Loves,
Maya