When you are next driving along and there is perhaps a car waiting to come out of a side road or something similar you will almost certainly look at the driver to get some indication or recognition that he has seen you, if your windows are blacked out that much that you cannot see the driver and therefore you cant be sure if he has seen you or not, I think you can see why the Police enforce tinting windows so dark you cant be seen also your insurance co will almost certainly wash their hands of any claims. Its for your safety and also your friends and family who may well be in your car.