Stop in for a cup of coffee

So thinking out loud here,

I was looking at my wife’s Durango and noticed that the entire front, the grille and the facia behind it, all gently angles towards the radiator. Even from underneath. I’m guessing this serves two purposes, drag coefficient reduction but all to better direct the air flow to the radiator and help with cooling.

So I’m wondering, why that couldn’t be done behind the grill of say my dart where there is nothing but a flat piece of metal for half the cubic feet of the front end? And would it have any noticeable effect