For an ICE vehicle weight reduction makes perfect sense, however for an EV it makes very little difference. This sounds counter intuitive and is probably why not a single EV manufacturer gets it. Not only because it is harder to reduce weight percentage wise from an EV due to the heavy battery.
At continuous speed the energy equals the total of all resistance, like:
air resistance, roll resistance, drive line resistance, motor losses, electrical losses etc.
Weight has no part in this equation, just indirect as it has some influence on the roll resistance.
When accelerating weight does play a big part, however an EV can recover the energy used for accelerating when decelerating. For accelerating/decelerating weight influence is dependent how efficient the regenerative system works. A theoretical 100% efficient regenerative breaking system will recover all energy used for accelerating.
It makes far more sense to focus on other aspects like: aerodynamics, low resistance bearings (air or magnetic), Vacuum motor, extreme high voltage batteries, good thermal insulation of cabin (to save HVAC energy), large solar panels area (a longer vehicle will also improve aerodynamics) and an efficient regenerative breaking system.
And for anyone who does not believe me, explain this:
Difference between a small and a large ICE vehicle is > 300% in fuel efficiency.
Difference between a small and a large EV is < 30% in energy efficiency.
(the 30% can mainly be explained by difference in: frontal area and tire width)
In general, I agree. From the data of the Knockout round at the Automotive X-Prize, I figured that the most important factor is drivetrain efficiency, and second is aerodynamic drag, then weight is third, and rolling friction and other misc losses.
http://neilblanchard.blogspot.com/2010/09/x-prize-knockout-round-cont.html
By the way, regenerative braking is more like 40-80% efficient. Coasting is the most efficient way to use the kinetic energy of the moving vehicle - electric cars have a big advantage here, too - no idling, and easy coasting. Unfortunately, only a few EVs have coasting by default, and some do not integrate regen on the brake pedal.
Weight always matters. Just ask my wife when my work truck needs a new set of tires. All kidding aside, if a vehicle's accelerations and decelerations were all along a perfect frictionless rail, we wouldn't need suspensions for one thing. But we have twisty roads and rough surfaces. The more the vehicle weighs, the larger and heavier all components need to be, ...the more energy is wasted in ALL accelerations, plus regenerative charging and normal battery charging. More energy is also lost maintaining optimal battery and cabin temperature. Larger wheel motors might require larger cowlings increasing frontal area. Not quite a death spiral, still, why go down bad paths. ...and more of all materials mean higher initial costs.
Drivetrain losses and aero drag losses - are always TOTAL losses. Weight losses can be partially regained in 2 ways: coasting, and regen.
The Aptera looks to be addressing ALL of these.