The problem with wheel motors has historically been unsprung mass (the mass of the portion of the car that moves with the wheel, rather than with the chassis --

The problem with wheel motors has historically been unsprung mass (the mass of the portion of the car that moves with the wheel, rather than with the chassis -- typically the tire, wheel, brakes, suspension upright, and half of the driveshafts, springs, dampers and suspension arms). The problem with unsprung mass is that it lowers the amount of available friction (for cornering, acceleration or braking) on bumpy roads. What happens is that the inertia of the unsprung mass as it's cresting a bump partially or completely offsets the downward force of the weight of the car, and the tire no longer has any normal force with which to create friction. A good active suspension can help by measuring the force of the tire on the road and attempting to keep it roughly constant (by actively shoving around the suspension). But historically active suspensions have been energy hogs, soaking up something like a liter of fuel per hundred kilometers. It's possible that newer power electronics and an attempt to actually focus on energy efficiency could reduce that, but it's likely to be expensive and complicated in any case.