And some clarifying, although unresponsive to the question, data courtesy of the SRT Engineers:
1. Removing the grills can allow unwanted hands to take the dip stick, oil fill cap and so on while the owner isn't looking.
2. The grills keep debris from getting under the hood and possibly causing issues. For example a few dry leaves in the right spot and you could have a fire when things heat up or a stone or other object could get into the accessory drive while driving and cause belt damage or loss. Another possibility is someone who intentionally drops something into your engine compartment while the car is unattended.
3. With the above said, the grills do not provide any kind of structural support to the hood. There is some improvement in cooling and front downforce by leaving the grills off.