Can confirm - recently was in a 1970 GM car and the windshield was covered in dead bug guts at the end of the drive. On the way home, my 2008 GM had nothing.
Insects fly at different height depending on time of day and weather. Did those conditions(time of day and weather) change much between your two trips?
It is not because of aerodynamics. Old and new cars smash insects equally efficient and the decline of smashed insects on windscreens correlates strongly with a decline in insect population.
