there are at least 2 good reasons.
the first is the same reason starters (and ring-gears) are replaced in forklifts so much more often than in cars, trucks and ag-equip. In a car you start the car an average of 3 times a day, in a forklift you may start the motor an average of 6 times a shift or more. In a car you may not even use the park brake, while in that forklift the park brake may be used 6 times an hour.
The other is the tendency to run over strapping and stretch wrap, that winds itself around the wheels and brake parts, causing all sort of problems