Air suspension gives you options. You can lower for a better look, reduce tire gaps and increase range.
You can raise to go off road, on dirt roads, in deep snow and help you get up steep driveways.
Raising a bit can make getting in and out easier for the less spry.
Great if you are going to be towing or carrying heavy loads. Will keep the headlights pointed straight ahead.
You can lower your car for less sway on curvy roads.
The Tesla system has geo-fencing. It remembers the level you prefer in different areas. If you need to raise it to get over a driveway hump, it will remember and raise it for you automatically every time you go there.
I lower my X to make it easier to wash it's roof, then raise it back up for easier cleaning of the lower valance.
With steel springs, you are locked into what ever ride height no matter what. As time goes by, steel springs will tend to sag, often unevenly.