Re: 80% of parts on electric cars have commonality with traditional cars
On a high performance car like the Tesla the motors are heavy and expensive.
Putting them in the wheels would be tricky, you don't want unecessary unsprung weight. Formula 1 cars (and 2CVs) even have the brakes mounted on the "axle" to reduce the weight of the bit bouncing up and down on the road.
So you need to mount two motors back-back in the middle each connected to a half shaft. But then you need careful control that you don't put even slightly more speed to one wheel than the other (torque steer), except when cornering when you DO need to put more speed to one than the other. It's easier to just mount a single motor to a regular differential.
If you want AWD then two motors back-back in the middle and sets of axles and diffs makes sense. Especially since AWD transmissions already have a central differential anyway.
If you want super go anywhere low speed AWD or just a low speed golf-buggy then a motor per wheel does have advantages.