I'm sure if you were to look at engine bay temps of the older engines vs the newer "High Strung" "High Power" engines of today, you would find its harder to keep the engine cooler these days.
With all the required radiators and inter-coolers, you need large openings on the front. You can only do so much with the lower air dams. As long as they keep them still aesthetically appealing along with the function they perform, I don't mind..
*Note: On the Previous Merc and on the M3, they have Horizontal Coolers to try get as many of them in front of the Airflow.
*Edit: Just look at how much surface area the M3 needs. For this they are going to continue offering larger openings to offer up airflow. I think its purely a design thing.