There are many reasons for that: 1) 'everyone else does it so it must be the best option' 2) slipper would catch on fire in one lap in a car that big 3) shares parts.

The theory behind a center diff in a tenth scale actually makes more sense than having one in an 1/8th scale if we were only talking about traction levels (not wear and tear), as it would allow the front and rear of the car to 'adapt' to the traction available and be as efficient as possible with the grip the small tires have.