2012 BMW 128i - Curtains for the 1-Series

Despite now hosting an M version, the normal BMW 1 Series range hasn’t been standing idle. The 2012 128i has a tweaked front end for improved aerodynamics on both its tin-top and convertible iterations. It’s actually called an Air Curtain that apparently reduces turbulence around the front wheel arches. Which brings to mind one general question about almost any sporty car that suddenly gets improved aerodynamics: Why didn’t engineers do that kind of thing when they had the car in the wind tunnel the first time around?