Well, if I remember correctly, the "correct" ride height I think is 4" from the bottom of the frame for the front, and 4 1/2 " for the rear. They do have adjustable coil over shocks. I know my cars have scrapes on the front body area below the
oil cooler ..
I would think the size of the tire can also contribute to the gap, obviously if the tire is undersized.
as far as why have some larger gaps, I'd guess you'd need to talk to the owners, or who ever set up the suspension.