I think most people think when we talk about tinting the front windshield of a car, they think we are putting a dark tint on it.
The "Legal" tinting of the front windshield if done with a film that has virtually no "light" cutting factors usually about 95%
thus, why do it... to reduce the heat and the UV light that enters the car. yes, its completely legal HERE IN HAWAII, and most of the Continental United States. (I say most because I am not going to google it)....
and yes, there are those people that do put 35% tint on the front windshield, which here in HAWAII is illegal here. Just like driving with out a front license being displayed. LOL