In fairness, it's not to protect the drivetrain - on 1/8th scale cars, they're solid as a rock - and there's the inherent problem - there's no give when using direct-drive. It's to protect the rotor, and make the car easier to drive over bumps and ruts.
Exponential prevents you from having a linear throttle curve, which I feel is more predictable and easier to drive as the speed and the throttle position are directly proportional.
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