Being forced to have a single engine, ICE cars need to rely on center differentials with a driveshaft. There are losses in the drivetrain, there is weight involved, and that shaft takes room in the middle of the car (the middle "hill"). To output the same power in a single motor, that motor would need to be bigger too. I'd say it's simpler to electronically control the difference in wheel speed from front to back and decide on power output based on available traction, on top of saving that hardware, to use two motors.