"Somebody" > wrote
> Again, if your air dam is plowing it, snow doesn't touch the underside of
> your car because it's flat.

Two things you have neglected in your discussion.
1) If you try to go through a drift, the front wheels are likely to plane
up on the more densely packed snow, then drop down the other side,
which puts the car into a teeter-totter on the drift.
2) A car is often higher in the front, either due to weight/loading,
or by weight shift (granted, small if you're a smart winter driver), or
by the action of the air dam deflecting snow downward.

FloydR