I think the move to aero rims come from a need to strengthen the rims for a lower spoke count, they are essentially an 'A' frame in section, which being fully triangulated is the lightest construction for the strength. Being able to advertise them as aerodynamic is an added bonus for the manufacturers.
I don't feel the rims themselves reduce drag, but the ability to go down on the spoke count does (marginally), so the rim's only contribution to aerodynamics is indirect.
My personal opinion is that you can spend thousands of hours in a wind tunnel designing a bike, but as soon as you throw a rider on it you have tossed all those hours right out the window.

Three more or less modern trends I dislike are the move to fatter tires, everything going to blackwall, and the whole 'aero' movement

Ken.