Two different things. Driving a farm truck on a rural road in Nebraska is very different from driving a tractor-trailer loaded in heavy traffic on the interstate.
And I assume you mean that navigating a farm truck in heavy traffic on a dirt road going into the co-op, sometimes waiting for 2 hours to dump the load, with tight busy traffic passing both ways on a narrow dirt road lined with ditches that could roll the vehicle is different than what you're saying.
My first job was at 12 years old; I drove a 6 wheeled grain truck for our family's farmer friend in the July heat to help with his wheat harvest.
No a/c, windows were stuck down, 3 speed. Bruce, the farmer, rigged up a pedal extension for me on the clutch.
Plenty of kids down here can drive a skid steer, tractor, truck, or loader.