this seems like a potential area for innovation; Self propelled consumer ICE lawnmowers are plagued by open differentials, front wheel drive, and a complex drive system (belt and clutch attaching to a constant speed motor)

Electrics, on the other hand, could easily have independent front and rear motors, if not each wheel; an independent ramping and traction control system from the main motor -- and even an isolated electrical system (via capacitor) such that grass load and wheel speed are indepedent.