Power
Physical power is a must. You need the muscle and the will to operate a 600-horsepower hunk of steel, plus lift and haul supplies and other equipment. You need stamina to stay alert behind the wheel. But there's not much political power to be found in this job. You answer to the man.
If your job title is industrial truck/tractor operator, the fact is you're probably not going to be anyone's boss. To some degree, you'll have to work independently and make your own decisions on the fly, but if you want to be the boss man, you'll have to put in the time and take a managerial position.