Um... Smarts aren't actually very aerodynamic... at least the Cd on the original ForTwo was 0,35, which is really bad. Being so short makes it very hard for them to get a good drag coefficient. Now, the quite low frontal area lowers the CdA (by lowering A), but still, they're nothing incredible when it comes to drag. And A is not the parameter you want to lower, because lowering A means sacrificing interior space.
To put into perspective how bad its drag coefficient is - the Tesla Model S 75D (higher drag coefficient, larger area, and less efficient motor than the Model 3) is EPA rated for 33kWh/mi - only 2kWh/mi more than the tiny Smart Fortwo Electric (31 kWh/mi). Almost every popular EV in the US today except for MS and MX have better EPA ratings than the Fortwo electric. Bolt is 28 kWh/mi. Leaf is 30 kWh/mi. Ioniq is 25 kWh/mi. Etc.
Secondly, as have been pointed out many times, saving money on your power bill is the least of reasons to improve efficiency. Improved efficiency means more range and/or smaller (cheaper) batteries (and the knock-on effects of reduced weight), a higher top speed (where not software limited; easier to hit the limited speed regardless), faster charge charging (in terms of mph / kph), fewer cycles, and more importantly, less deep daily cycles.
And yes, it also saves you a small amount of money directly on your power bill, but that's probably the least important aspect of the above.
To put a dollar figure on just the range aspect: the difference in drag between the 18" aeros and 19" "sport" wheels is reported to be 10%, which means about a 7% difference in range. A 41% difference in range (LR vs. SR) costs $9k. So the range aspect comes in at a value of $1540 - 4,5% of the entire vehicle's MSRP. That's just range we're talking about - how do you value other things - say, faster charging (distance per unit time connected)?
