Some look close to like a real car, that one EV + solar, 25miles/KWh https://en.wikipedia.org/wiki/UNSW_Sunswift#/media/File:Suns...

I'd venture a guess - Aptera went for 3 wheeler because certification as a motorcycle is much easier than as a 4-wheel car. Unfortunately 3 wheels - 3 vertical columns resisting the upcoming air - may be less aerodynamic than 4 wheels which are only 2 vertical columns resisting the upcoming air. Add to that that for the same stability you generally need the paired wheels in a 3 wheeler wider than the paired wheels in a 4 wheeler - that again worsens the 3-wheeler aerodynamics.

Having worked on one of the cars for this, I don't think solar panels on cars actually makes much sense for useful cars. If you can put them on cheaply enough, then they are maybe a nice free boost in some circumstances, but the compromises in the design needed to get the efficiencies necessary for solar panels on the car to power the car are quite extreme.