[Blue Bomber Man]

Just because aerodynamics/drag becomes the main source of loss energy, does not mean you are losing any less at the tires.

Think of the energy loss as a pie, and say 80% is loss at the engine (typical value, I can cite sources later if you want), at urban speeds, tire losses will count for around 7% and aero is 6% and the rest is lost in drive train and suspension.

When you reach highway speeds, the energy loss pie gets bigger, the amount of energy loss by the tires, engine and drive train remain the same (or similair), but aero losses increase.

So you still get the same reduction of energy waste at higher speeds, its just less noticeable compared to loss due to aerodynamics.