At least in the USA, it's probably due to having been alive long enough for sun damage to cause a freckle on the side of your body nearest the car window while driving.
I mean... I've never driven a vehicle that didn't have tinted windows (the heat reduction benefits are huge), but then the sun wants me dead anyway; I spent a week in a southern state and suddenly had freckles in places that never saw the sun.
I’ve had mine since before I started driving ¯\_(ツ)_/¯
I noticed in my late teens I had a lot of freckles on the left side of my body and very few on the right, and I didn’t start driving until I was 22. I did spend 2 years in high school with a much darker tan on my right arm from hanging my arm out the window of a boyfriend’s car with no AC, but still have more left-arm freckles.