The rationale is, many crashes happen at dusk or in the dark, and an outsized number on unlit roads. While almost all modern headlights outperform the dim, unfocused sealed beams of the past, IIHS says that government regulations aren't doing a good enough job of ensuring real-world performance. Adaptive headlights turn with the front wheels, helping out a lot in IIHS's tests on illumination in sharp and gradual curves.
The Adaptive Front-Lighting System is only available in the Grand Touring Reserve and Signature trim levels, meaning that you'll have to upgrade to those fancy versions to get it. It'd be nice if Mazda allowed even lower-trim buyers to add this as a stand-alone option, but for now that's not how it works.
Fancy, safer headlights or no, we love the new Mazda6, especially the turbocharged version. It's one of the most fun sedans around. And, according to IIHS, now one of the safest.