My hypothesis is better wind tunnel testing for modern cars so that the bugs go over instead of splatting.

> The second survey, in the UK county of Kent in 2019, examined splats in a grid placed over car registration plates, known as a “splatometer”. This revealed 50% fewer impacts than in 2004. The research included vintage cars up to 70 years old to see if their less aerodynamic shape meant they killed more bugs, but it found that modern cars actually hit slightly more insects.

https://www.theguardian.com/environment/2020/feb/12/car-spla...

I'd go with fewer people having experience driving not in a city, at least in this forum making the claims as GP